Engine Controls Self-Diagnostics - 3.4l — Chevrolet Impala VIII (1999-2006)

MODEL IDENTIFICATION

Vehicle model is identified by the fifth character of Vehicle Identification Number (VIN). VIN is stamped on metal pad on top of left end of instrument panel, near windshield. See MODEL IDENTIFICATION table.

Series (1)	Model
"N"	Alero & Grand Am
"W"	Impala & Monte Carlo
(1) Vehicle series is fifth character of VIN.

(1)	Vehicle series is fifth character of VIN.

MODEL IDENTIFICATION

INTRODUCTION

To properly diagnose and repair this vehicle, follow DIAGNOSTIC PROCEDURE under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to appropriate BASIC DIAGNOSTIC PROCEDURES article. If no DTCs are present and a driveability condition exists, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

ON-BOARD DIAGNOSTICS

PCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM will store a Diagnostic Trouble Code (DTC) and, if code is emissions related, the Malfunction Indicator Light (MIL) located on instrument cluster will illuminate.

There are 2 paths for accessing on-board diagnostics. It is necessary to access information through both paths, as each path presents some different information.

Generic OBD-II This provides all generic codes and some OEM codes, serial data required for generic OBD-II and some OEM PIDs, monitor status, pending codes and freeze frame.
OEM All DTCs, all PIDs, failure records, enhanced scan tool information and all other OEM scanner functions.

Code Types

There are 4 types of DTC categories

Type "A" Emissions related. Illuminates MIL the first time DTC sets.
Type "B" Emissions related. Illuminates MIL if fault is active for 2 consecutive driving cycles.
Type "C" Non-emissions related. Does not illuminate MIL, but will illuminate SERVICE light.
Type "D" Non-emissions related. Does not illuminate MIL or SERVICE light.

Freeze Frame/Failure Records

PCM stores one freeze frame record for the first failed test that sets a DTC and illuminates MIL. Freeze frame will not be overwritten unless a misfire or fuel trim DTC is set. Failure records are stored when any DTC is set. Some PCMs can store up to 5 failure records. Failure records will be stored for all types of codes, whether or not the MIL is illuminated.

Typical data includes

Air/fuel ratio.
Airflow rate.
Fuel trim.
Engine speed.
Engine load.
Engine coolant temperature.
Vehicle speed.
Throttle position angle.
Manifold absolute pressure.
Injector base pulse width.
Loop status.

Monitors

Comprehensive Component Monitor Monitors PCM systems for opens, shorts, grounds and out-of-range sensors. Also monitors rationality of sensors. Rationality is whether the sensor's value is consistent with operating conditions of the other sensors.
Misfire Monitor Monitors engine misfire using crankshaft sensor to determine location and severity of misfire. A catalyst damaging misfire will flash the MIL, and a non-catalyst damaging misfire is a normal type "B" code.
Fuel Trim Monitor Monitors short and long term fuel trim for being at maximum lean or rich limit.
Oxygen Sensor Monitor Monitors all oxygen sensors for maximum voltage level, minimum voltage level and lean rich/rich lean switching rate.
Oxygen Sensor Heater Monitor Monitors oxygen sensor heater by watching sensor's time-to-activity after a cold start.
Catalyst Monitor Monitors catalyst efficiency by comparing activity rate of pre-catalyst oxygen sensor and post-catalyst oxygen sensor.
EVAP Monitor Monitors EVAP system for large leaks, small leaks and purge flow.

INTERMITTENT CONDITIONS

Note. Intermittent is a DTC or symptom, with a condition that cannot be duplicated.

Preliminary

Perform the Diagnostic System Check - Engine Controls before starting. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .

Harness or Connector Intermittents

Many intermittent open or shorted circuits come and go with harness or connector movement caused by the following type conditions

Vibration.
Engine torque.
Bumps or rough pavement.

Test for intermittents by performing the applicable procedure from the following list

Move related connectors and wiring while monitoring the appropriate scan tool data.
Move related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the component operation.
With the engine running, move related connectors and wiring while monitoring engine operation.

Verify whether the harness or connector movement affects any of the following systems

Data displayed.
Component or system operation.
Engine operation.

Repair the components as necessary.

Electrical Connections or Wiring

Intermittents are usually caused by one or more of the following conditions: Poor electrical connections. Terminal tension. Wiring problems.
Carefully inspect the suspected circuit for the following conditions: Poor mating of the connector halves. Terminals backed out or not fully seated in the connector body. Improperly formed or damaged terminals. Test for poor terminal tension. Poor terminal to wire connections including terminals crimped over insulation. This requires removing the terminal from the connector body. Corrosion or water intrusion. Pierced or damaged insulation can allow moisture to enter the wiring. The conductor can corrode inside the insulation, with little visible evidence. Look for swollen and stiff sections of wire in the suspect circuits. Wires that are broken inside the insulation. Pinched, cut, or rubbed through wiring in the harness. Wiring that is in contact with hot exhaust components.
Repair the condition as necessary.

Control Module Power & Grounds, & Component Power & Grounds

Poor power or ground connections can cause widely varying symptoms.

Test all control module power circuits. Many vehicles have multiple circuits supplying power to the control module. Other components in the system may have separate power circuits that may also need to be tested. Inspect connections at the module or component connectors, fuses, and any intermediate connections between the power source and the module or component. A test light or a Digital Multimeter (DMM) may indicate that voltage is present, but neither tests the ability of a circuit to carry sufficient current. Ensure that the circuit can carry the current necessary to operate the component. See appropriate WIRING DIAGRAMS article.
Test all control module ground and system ground circuits. The control module may have multiple ground circuits. Other components in the system may have separate grounds that may also need to be tested. Inspect grounds for clean and tight connections at the grounding point. Inspect the connections at the component and in splice packs, where applicable. Ensure that the circuit can carry the current necessary to operate the component. See appropriate WIRING DIAGRAMS article.

Temperature Sensitivity

An intermittent condition may occur when a component or connection reaches normal operating temperature. The condition may occur only when the component or connection is cold, or only when the connection is hot.
The following data may help to diagnose this type of intermittent condition: Freeze Frame/Failure Records. Scan tool snapshot. Vehicle data recorder.
If the intermittent is related to heat, review the following data: High ambient temperatures. Underhood or engine generated heat. Circuit generated heat due to a poor connection, or high electrical load. Higher than normal load conditions, such as towing.
If the intermittent is related to cold, review the following data: Low ambient temperatures. In extremely low temperatures, ice may form in a connection or component. Test for water intrusion. The condition only occurs on a cold start. The condition is not present after the vehicle warms up.
Information from the customer may help to determine if the trouble follows a pattern that is temperature related.

Electromagnetic Interference (EMI) and Electrical Noise

Some electrical components or circuits are sensitive to EMI or other types of electrical noise. Perform the following procedures

Inspect for a misrouted harness that is too close to a high voltage or high current device. This condition may induce electrical noise on a circuit that could interfere with normal circuit operation. Inspect for wires that are too close to the following devices: Secondary ignition components. Motors. The generator.
Determine whether the electrical system interference is caused by a malfunctioning relay, PCM driven solenoid or switch. These components may cause a sharp electrical surge. Normally, the problem will occur when the malfunctioning component is operating.
Determine whether non-factory or aftermarket add-on accessories are installed in the vehicle. These accessories may lead to an emission related OBD-II failure. Determine if any of the following non-factory or aftermarket add-on accessories is causing the intermittent: Lights. 2-way radios. Amplifiers. Electric motors. Remote starters. Alarm systems. Cell phones.
Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode.
Test for proper performance of the generator. See ON-VEHICLE TESTING in appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
If a DTC is determined to be intermittent, and the tests in this section do not reveal a problem, see «VEHICLE DATA RECORDER»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__vehicle-data-recorder) .

Incorrect PCM Programming

There are only a few situations when reprogramming a PCM is appropriate, such as the following: A new service PCM is installed. A PCM from another vehicle is installed. Revised software or calibration files have been released for this vehicle. NOTE: DO NOT reprogram the PCM with the SAME software or calibration files that are already present in the PCM. This is not an effective repair for any type of driveability problem.
Verify that the PCM contains the correct software or calibration. If incorrect programming is found, reprogram the PCM with the most current software or calibration. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING.

Duplicating Failure Conditions

If none of the previous tests are successful, attempt to duplicate or capture the failure conditions.
Freeze Frame/Failure Records data, where applicable, contains the conditions that were present when the DTC set. Perform the following procedure: Review and record Freeze Frame/Failure Records data. Clear the DTCs using the scan tool. Turn the key to OFF and wait 15 seconds. Operate the vehicle under the same conditions that were noted in Freeze Frame/Failure Records data, as closely as possible. The vehicle must also be operating within the Conditions for Running the DTC. Monitor DTC Status for the DTC being tested. The scan tool will indicate Ran, when the enabling conditions have been satisfied long enough for the DTC to run. The scan tool will also indicate whether the DTC passed or failed.
An alternate method is to drive vehicle with the Digital Multimeter (DMM) connected to a suspected circuit. An abnormal reading on the DMM when problem occurs, may help you locate the problem.

Scan Tool Snapshot

The scan tool can be set up to take a snapshot of the parameters available via serial data. The snapshot function records live data over a period of time. The recorded data can be played back and analyzed. The scan tool can also graph parameters singly or in combinations of parameters for comparison. The snapshot can be triggered manually at the time the symptom is noticed, or set up in advance to trigger when a DTC sets. An abnormal value captured in the recorded data may point to a system or component that needs to be investigated further. Refer to scan tool user instructions for more information on the Snapshot function.

Vehicle Data Recorder

The J-42598 Vehicle Data Recorder is connected to the data link connector (DLC) and sent with the customer. The J-42598 captures data for later retrieval and analysis by the technician. Refer to the vehicle data recorder user instructions for more information.

DIAGNOSTIC PROCEDURE

Diagnosis of computerized engine control system should be performed in the following order

Ensure all engine systems not related to computer system are operating properly. DO NOT proceed with testing unless all other problems have been repaired. Diagnostic system check must be performed before using specific DTC testing procedure. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) .
If no DTCs are present and a driveability problem exists, refer to SYMPTOMS in appropriate TROUBLE SHOOTING - NO CODES article. Doing so will help identify proper system or component to check in appropriate SYSTEM & COMPONENT TESTING article.
After necessary repairs are made, clear DTCs, verify vehicle will enter "closed-loop" operation and ensure DTC does not reset.

RETRIEVING DIAGNOSTIC TROUBLE CODES

DTCs are retrieved using a Tech 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC). (Scheme 1) See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS. DLC is located below left side of dash.

Scheme 1

Scheme 1: RETRIEVING DIAGNOSTIC TROUBLE CODES

DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS

Note. Check for applicable Technical Service Bulletins (TSB) before proceeding. DO NOT perform the following procedure if driveability conditions are not present. DO NOT turn ignition off during the following procedure or clear DTCs unless instructed to do so.

Description

The Diagnostic System Check - Engine Controls is an organized approach to identifying a condition that is created by a malfunction in the engine control system. The diagnostic system check must be the starting point for any driveability concern. The diagnostic system check directs the service technician to the next logical step in order to diagnose the concern. Understanding and correctly using the diagnostic procedure reduces diagnostic time and prevents replacement of good parts.

Test Description

The numbers below refer to the step numbers in the diagnostic procedure.

2 Lack of communication may be due to a malfunction of the serial data circuit, the control module, or the scan tool. The specified procedures in Data Link Communications will determine the particular condition.
5 This step stores the PCM DTC information into the scan tool memory. Review the captured information at the end of the diagnostic procedure in order to catch the next DTC in the event there are multiple DTCs stored. Use this information in order to determine how frequently and how recently the DTC set. This information and other operating conditions when the DTC set may help diagnose an intermittent condition. Capturing the stored information preserves data that the PCM loses when the following occurs: When you are instructed to clear the DTCs. PCM connectors are disconnected. PCM is replaced during a diagnostic procedure or a repair procedure.
6 The presence of DTCs which begin with "U", indicate that some other control module is not communicating. Following the specified procedure will gather all the available information before you perform the tests.
8 If there are other control modules with DTCs set, refer to the DTC list. The DTC list directs you to the appropriate diagnostic procedure. If the control module stores multiple powertrain DTCs, diagnose the DTCs in the following order: Component level DTCs, such as sensor DTCs, solenoid DTCs, and relay DTCs. Diagnose the multiple DTCs within this category in numerical order. Begin with the lowest numbered DTC, unless the diagnostic table directs you otherwise. System level DTCs, for example, misfire DTCs, fuel trim DTCs, and catalyst DTCs.
10 This step is for areas that have inspection and maintenance testing procedures for emissions testing. Use this step if the testing facility found one or more I/M system statuses that did not set.

Diagnostic Procedures

Install scan tool. Does the scan tool power-up? If yes, go to next step. If no, perform SCAN TOOL DOES NOT POWER UP IN DATA LINK COMMUNICATIONS in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
Turn ON ignition, with engine OFF. Attempt to establish communication with the PCM, Body Control Module (BCM), Instrument Panel (IP) cluster, and Electronic Brake Control Module (EBCM). If you are using a Tech 2, obtain the information using the Class 2 Message Monitor feature. Does the scan tool communicate with all of the control modules? If yes, go to next step. If no, perform SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
Attempt to start engine. Does engine start and idle? If yes, go to next step. If no, go to NO-START DIAGNOSIS in appropriate BASIC DIAGNOSTICS PROCEDURES article.
Select the DTC display function for the PCM, BCM, IP cluster and EBCM. Does scan tool display any DTCs? If yes, go to next step. If no, go to step 9 .
With a scan tool, select Captured Info in order to store the powertrain DTC information. When complete, go to next step.
Does scan tool display DTCs which begin with a "U"? If yes, go to next step. If no, perform SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE appropriate BASIC DIAGNOSTICS PROCEDURES article.
Does scan tool display DTC P0601or P0602? If yes, go to «DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 OR P1683: CONTROL MODULE READ ONLY MEMORY»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0601-p0607-p1600-p1621-p1627-p1680) . If no, go to next step.
Does scan tool display DTC P0560 or P0620? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Is customer's concern related to the automatic transmission? If yes, diagnose transmission. See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If no, go to next step.
Is customer's concern with Inspection/Maintenance (I/M) testing? If yes, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) under INSPECTION/MAINTENANCE PROCEDURES. If no, go to next step.
Check for the following symptoms: Hard start, surges/chuggles, lack of power, sluggishness/sponginess, detonation/spark knock, hesitation, sag, stumble, cuts out, misses, poor fuel economy, poor fuel fill quality, rough idle, unstable idle, incorrect idle, stalling, dieseling, run-on, backfire, Malfunction Indicator Light (MIL) inoperative, or MIL always on. Did you find and correct the condition? If yes, system is okay. If no, problem is intermittent. See «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

CLEARING DIAGNOSTIC TROUBLE CODES

There are 3 methods to clear DTCs.

Scan Tool

Scan tool is preferable way to clear DTC information. Freeze frame and failure record data will also be cleared. PCM adaptive learning and system monitors will only be cleared for those system which had a stored DTC.

Disconnect Battery

Note. On many OBD-II systems, PCM will retain memory for an extended period of time with battery disconnected. Memory may be retained for several days.

Disconnecting PCM power or battery ground will clear all PCM memory including DTCs, freeze frame, failure records, adaptive learning and system monitors.

Warm-up Cycles

If fault that caused DTC to set is repaired, PCM will begin to count warm-up cycles. After 40 consecutive warm-up cycles with no further faults, PCM will automatically clear DTC from memory.

SCAN TOOL USAGE

Scan tool is a specialized tester which, when connected to DLC, can be used to diagnose on-board computer control systems by providing instant access to circuit voltage information without need to crawl under dash or hood to backprobe sensors and connectors.

Scan tool reduces diagnostic time dramatically by furnishing input data (voltage signals) which can be compared to specification parameters. They may also furnish information on output device (solenoids and motors) status. However, status parameters only indicate output signals have been sent to devices by PCM; they do not indicate whether devices have responded properly to signal. Verify proper response at output device using a voltmeter or test light.

A problem may exist even if DTCs are not present. Many driveability problems occur without setting DTCs.

Using a scan tool is the easiest method of checking sensor specifications and other data parameters. Scan tool is also useful in finding intermittent wiring problems by wiggling wiring harnesses and connections (key on, engine off) while observing data parameters.

Note. If erroneous voltage signals are suspected, verify tester information using a digital voltmeter and wiring schematic. If non-existent codes are displayed, DO NOT use scan tool for diagnosis. Contact tester manufacturer for additional information.

PCM LOCATION

PCM is located on right rear of engine compartment, near firewall.

PROGRAMMING

Note. For additional diagnostic information, refer to DTC P1336: CRANKSHAFT POSITION SYSTEM VARIATION NOT LEARNED .

CKP SYSTEM VARIATION LEARN PROCEDURE

Install a scan tool.
Using scan tool, monitor the PCM for DTCs. If other DTCs are set, except DTC P1336, refer to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) .
With a scan tool, select the CKP variation learn procedure.
Observe fuel cut-off for the engine that you are performing the learn procedure on.
The scan tool instructs you to perform the following: Block drive wheels. Apply vehicles parking brake. Cycle ignition from OFF to ON. Apply and hold the brake pedal. Start and idle the engine. Turn OFF the A/C. Place transmission in Park (A/T) or Neutral (M/T). The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components: CKP sensors activity. If there is a CKP sensor condition, refer to the applicable DTC that set. CMP sensor activity. If there is a CMP sensor condition, refer to the applicable DTC that set. ECT sensor activity. If ECT is not warm enough, idle engine until ECT reaches the correct temperature.
With the scan tool, enable the CKP system variation learn procedure.
Slowly increase engine speed to the RPM that you observed.
Immediately release the throttle when fuel cut-off is reached.
The scan tool displays Learn Status: Learned this ignition. If scan tool does NOT display this message and no additional DTCs set, diagnose for and engine mechanical problem. If a DTC is set, refer to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . Diagnose affected DTC(s).
Turn ignition off for 30 seconds after the learn procedure is completed successfully.

ENGINE OIL LIFE RESET

Using Radio

Turn the ignition to ACC OR ON, with the radio off.
Press and hold the TUNE DISP button on the radio for at least five seconds until SETTINGS is displayed.
Press the SEEK PTYPE or the SEEK PSCAN up or down arrow to scroll through the main menu.
Scroll until OIL LIFE appears on the display.
Press the 1 PREV or 2 NEXT button to enter the sub menu. RESET will be displayed.
Press the TUNE DISP button to reset. A chime will be heard to verify the new setting and DONE will be displayed for one second.
Once the message has been reset, scroll until EXIT appears on the display.
Press the TUNE DISP button to exit programming. A chime will be heard to verify the exit.

Using Accelerator Pedal

Turn ignition to ON, with engine off.
Fully press and release accelerator pedal 3 times within five seconds. If CHANGE ENGINE OIL message flashes, the system is reset. However, if it stays on, it did not reset. Repeat the procedure.

POWERTRAIN CONTROL MODULE

After replacing Powertrain Control Module (PCM) or if program needs to be updated, refer to latest Techline information on PCM reprogramming. PCM can only be programmed using Tech 2(tm) and Techline terminal, or by using a personal computer equipped with the current service programming system software installed.

Remote Programming

Before Programming A Control Module Ensure The Following Conditions Are Met

Vehicle system voltage: Ensure there is no charging system concern. All charging system concerns must be repaired before programming a control module. Ensure battery voltage is greater than 12 volts but less than 16 volts. The battery must be charged before programming the control module if the battery voltage is low. Ensure battery charger is NOT connected to the vehicle's battery. Incorrect system voltage or voltage fluctuations from a battery charger, may cause programming failure or control module damage. Turn OFF or disable the following system that may put a load on vehicle's battery. Twilight sentinel. Interior lights. Daytime Running Lights (DRL). Applying parking brake, on most vehicles, disable the DRL system. See owner's manual. Heating, Ventilation and Air Conditioning (HVAC) systems. Engine cooling fans, etc.
The ignition switch is in the proper position. The scan tool prompts you to Turn ignition on, with engine off. DO NOT change the position of the ignition switch during the programming procedure, unless instructed to do so.
All tool connections are secure. HVAC charging station. The connection at the Data Link Connector (DLC). Voltage supply circuits.
DO NOT disturb the tool harnesses while programming. If an interruption occurs during the programming procedure, programming failure or control module damage may occur.

Remote Programming

Turn ignition off.
Install the Tech 2(tm) to the data link connector (DLC).
Turn ignition on, with engine off.
Turn OFF all vehicle accessories.
With the Tech 2(tm), select Service Programming.
Identify vehicle information as requested by the Tech 2(tm).
Select the type of module you are programming.
Select the type of programming to be performed.
Verify the displayed VIN with the vehicle VIN. If the displayed VIN does not match the actual VIN, write down the actual VIN and correct the VIN at the Techline(tm) terminal.
When complete, exit Service Programming.
Turn OFF the Tech 2(tm) and disconnect the Tech 2(tm) from the vehicle.
Turn ignition off.
Connect the Tech 2(tm) to the Techline(tm) terminal.
Select Service Programming.
Select Tech 2(tm) as the tool you are using.
Select the type of programming to be performed.
Verify the displayed VIN with the vehicle VIN. Correct the VIN as necessary.
Select the type of module you are programming.
Identify what type of programming that you are performing. Normal. This type of programming is for updating an existing calibration or programming a new controller. Vehicle Configuration Index (VCI). This selection is used if the vehicle VIN is unavailable or not recognized by the Techline(tm) terminal. You will need to contact the Techline(tm) Customer Support center to use this option. Reconfigure. This is to reconfigure a vehicle, such as tire size and axle ratio changes.
Select the appropriate calibration file.
Ensure all connections are secure.
Select Reprog to initiate the download of the new calibration to the Tech 2(tm).
After the download is complete, turn OFF the Tech 2(tm).
Disconnect the Tech 2(tm) from the Techline(tm) terminal.
Install the Tech 2(tm) to the Data Link Connector (DLC).
Turn ON the Tech 2(tm).
Turn ignition on, with engine off.
Select Service Programming.
Select Program.
After the download is complete, EXIT Service Programming.
Turn ignition off for 30 seconds.
Turn OFF the Tech 2(tm).
If a control module is replaced the following service procedures must be performed: CKP System Variation Learn Procedure. See «CKP SYSTEM VARIATION LEARN PROCEDURE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__ckp-system-variation-learn-procedure) . Oil Life System - Resetting. See «ENGINE OIL LIFE RESET»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__engine-oil-life-reset) . Inspection/Maintenance (I/M) Complete System Set Procedure. See «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Programming. Theft Deterrent System. See «THEFT DETERRENT PASSWORD LEARN PROCEDURE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__theft-deterrent-password-learn-procedure) .

Programming Verification

With a scan tool, clear DTCs.
Attempt to start engine.
Repeat the Service Programming procedure if the engine does not start or operates poorly. Perform the following procedures before programming the PCM: Ensure the control module and DLC connections are okay. Ensure the Techline(tm) operating software is up to date. Ensure the calibration part number is correct for the vehicle.
Attempt to program the control module. If the control module still cannot be programmed properly, replace the control module. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. You must program the replacement control module.

Off-Board Programming

Note. DO NOT program a control module unless you are directed by a service procedure or you are directed by a technical service bulletin. Programming a control module at any other time will not permanently correct a customer's concern. The Off-Board Programming is used in situations where a control module must be programmed without having the vehicle present. The Off-Board Programming Adapter must be used to perform the Off-Board Programming procedure. The adapter allows the control module to power up and allows the Tech 2(tm) to communicate with the control module. DO NOT disturb the tool harnesses while programming. If an interruption occurs during the programming procedure, programming failure or control module damage may occur.

Before Programming a Control Module

Ensure that all connections are secure at the following locations: The Off-Board Programming Adapter. The Tech 2(tm). The control module. The Techline(tm) terminal.

Off-Board Programming

Obtain the VIN of the vehicle for which the control module is being programmed.
With the Techline(tm) terminal, select Service Programming.
Select Tech 2(tm), Reprogram ECU, and Off-Board Programming Adapter as the ECU location.
Connect control module, Off-Board Programming Adapter, and Tech 2(tm) as described on the Techline(tm) terminal. Ensure you use the correct harness connector from the Off-Board Programming Adapter kit.
With the Tech 2(tm), select Service Programming Request Information function. The Tech 2(tm) communicates with the control module and receives the access code.
With the Tech 2(tm), exit the Service Programming Request Information.
Disconnect the Tech 2(tm) from the Off-Board Programming Adapter.
Connect the Tech 2(tm) to the Techline(tm) terminal.
Turn ON Tech 2(tm).
With Techline(tm) terminal, enter VIN of the vehicle that will be receiving the control module.
The Techline(tm) terminal will display the message, attaching to database.
Identify what type of programming that you are performing.
Select the appropriate calibration file.
Ensure all connections are secure.
The Techline(tm) terminal displays a summary screen that summarizes your selections. After confirming you choices, the Techline(tm) terminal automatically loads the calibration files to the Tech 2(tm).
After the download is complete, turn OFF the Tech 2(tm).
Disconnect the Tech 2(tm) from the Techline(tm) terminal.
Connect the Tech 2(tm) to the Off-Board Programming Adapter.
With the Tech 2(tm), select Service Programming.
With the Tech 2(tm), select Program.
After the download is complete, exit Service Programming.
Turn OFF the Off-Board Programming Adapter.

THEFT DETERRENT PASSWORD LEARN PROCEDURE

Note. The Body Control Module (BCM) must be programmed with the proper RPO configurations before performing learn procedures. See PROGRAMMING in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If replacing the BCM with a GM Service Parts Operations (SPO) replacement part, the module will learn Passlock(tm) sensor data code immediately. The existing PCM however, must learn the new fuel continue password when the BCM is replaced. If replacing a PCM with a GM Service Parts Operations (SPO) replacement part, after programming, these modules will learn the incoming fuel continue password immediately upon receipt of a password message. Once a password message is received, and a password is learned, a learn procedure must be performed to change this password again. A PCM which has been previously installed in another vehicle will have learned the other vehicle's fuel continue password and will require a learn procedure after programming to learn the current vehicle's password.

Use this procedure after replacing

Passlock(tm) Sensor
BCM
PCM

10-Minute Learn Procedure

Note. This procedure requires a Tech 2 scan tool and a Techline(tm) terminal with current Service Programming System (SPS) software.

Connect the Tech 2 to the vehicle.
Select Request Information under Service Programming.
Disconnect the Tech 2 from the vehicle and connect it to a Techline(tm) terminal.
On the Techline(tm) terminal, select Theft Module Re-Learn under Service Programming.
Disconnect the Tech 2 from the Techline(tm) terminal and connect it to the vehicle.
Turn ignition on, with engine off.
Select VTD Re-Learn under Service Programming.
Attempt to start the engine, then release the key to ON (vehicle will not start).
Observe the SECURITY telltale, after about 10 minutes the telltale will turn OFF (vehicle is now ready to relearn the Passlock(tm) Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK).
Turn ignition off, and wait 5 seconds.
Start engine (vehicle has now learned the password).
With the Tech 2 (scan tool), clear any DTCs.

30-Minute Learn Procedure

Turn ignition on, with engine off.
Attempt to start engine, then release key to ON (vehicle will not start).
Observe the SECURITY telltale, after about 10 minutes, the telltale will turn OFF.
Turn ignition off, and wait 5 seconds.
Repeat steps 1 - 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the Passlock(tm) Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK).
Start engine (vehicle has now learned the Passlock(tm) Sensor Data Code and/or password).
With a scan tool, clear any DTCs if needed (history DTCs will self clear after 100 ignition cycles).

DRIVE CYCLES

Note. See INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE .

Several states require that a vehicle pass On-Board Diagnostic (OBD) system tests and I/M emission inspection in order to renew license plates. This is accomplished by viewing the I/M SYSTEM STATUS display on scan tool. Using a scan tool, the technician can observe the I/M System Status in order to verify that vehicle meets the criteria that complies with the local area requirements.

Conditions For Updating I/M System Status

Each system requires at least one, and sometimes several, diagnostic tests. The results of these tests are reported by a Diagnostic Trouble Code (DTC). A system monitor is complete when either all of the DTCs comprising the monitor have Run and Passed, or any one of the DTCs comprising the monitor have illuminated the MIL. Once all of the tests are completed, the I/M System Status display will indicate YES in the Completed column. For example, when the HO2S Heater Test indicates YES, all of the oxygen sensor heaters have been diagnosed. If the vehicle has 4 heated oxygen sensors, all 4 heater circuits have been diagnosed. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
The battery has been disconnected or discharged below operating voltage.
The control module power or ground has been interrupted.
The control module has been reprogrammed.
The control module DTCs have been cleared as part of a service procedure.

Monitored Emission Control Systems

The OBD-II system monitors all emission control systems that are on-board. Not all vehicles have a full complement of emission control systems. For example, a vehicle may not be equipped with AIR or EGR. The OBD-II regulations require monitoring of the following

Air conditioning system.
Catalytic converter efficiency.
Comprehensive component monitoring - emission related inputs and outputs.
Evaporative Emissions (EVAP) system.
Exhaust Gas Recirculation (EGR) system.
Fuel Delivery system.
Heated catalyst monitoring.
Misfire monitoring.
Oxygen Sensor (O2S or HO2S) system.
Oxygen Sensor Heater (HO2S Heater) system.
Secondary Air Injection (AIR) system.

For the specific DTCs required for each system, refer to INSPECTION/MAINTENANCE SYSTEM DTCS . Systems such as fuel delivery, misfire, and comprehensive components may not be listed in a system status list. These tests run continuously on some vehicles and may not require an indicator.

1 Any DTCs set, even those that are not listed in the Inspection/Maintenance System DTCs, may prevent the required DTCs from running. If there is any question as to whether a set DTC is disabling the required I/M diagnostic, review the Conditions for Running in the diagnostic procedures for the DTC required by the I/M diagnostic. A list of disabling DTCs, if applicable, is contained in the supporting text for that DTC.
2 Anytime a control module is reprogrammed or the diagnostic trouble codes are cleared as part of a repair procedure, all the I/M System Status indicators will reset to NO.
3 Use discretion when determining whether the entire system set procedure needs to be performed. For example, if the only tests that have not run are those that require the engine to be at operating temperature, then only those individual tests need to be run. There is no need to allow the engine to completely cool in order to run these tests.

Note. Many DTC related repairs will instruct the technician to clear the DTC information. This procedure will reset ALL of the I/M System Status indicators to NO, and require performing the I/M Complete system Set Procedure.

Perform powertrain diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. Repair any DTCs or driveability concerns that would prevent the I/M System Status tests from completing. Did you find and repair a DTC or driveability concern? If yes, go to step 3 . If no, go to next step.
Review any service bulletins for software updates that may prevent I/M readiness. Perform any reprogramming or repairs indicated by the service bulletins. Was a repair service required? If yes, go to «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go next step.
Using scan tool, observe the I/M System Status display. Is more than one test indicating a NO status? If yes, go to «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to appropriate INSPECTION/MAINTENANCE SYSTEM SET procedure for the indicated system.

Diagnostic Aids

The I/M System Status display provides an indication of when the control module has completed the required tests. This does not necessarily mean that the test has passed, only that a decision was made. If the diagnostic fails, a DTC will indicate the failure. If a failure indication is present for a DTC associated with one of the I/M regulated systems, it may prevent other required tests from running. For example, a DTC for the control circuit of the relay controlling an AIR pump may not be listed in the Inspection/Maintenance System DTCs because it is a continuous test. If this DTC is set, the Active Tests for the AIR system may not run.

The I/M System Status information may be useful for a technician to determine if diagnostics have run when verifying repairs.

This procedure satisfies enable criteria necessary to execute all monitor diagnostics, and complete trips for those particular diagnostics. When all diagnostic tests have been completed, I/M system status indicators are set to YES. Perform this test when more than one or all I/M system status indicators are set to NO.

Conditions For Running (Cold Start)

Ensure vehicle meets the following conditions before performing procedure

Barometric pressure is greater than 19.2 in. Hg (65 kPa).
Engine coolant temperature is less than 86°F (30°C).
The Intake Air Temperature (IAT) is less than 90°F (32°C).
The difference between IAT and ECT is 7°F (5°C) or less.
Battery voltage is 10-18 volt
Fuel level is 1/4-3/4 tank.

Test will initiate only after a cold start. A cold start is considered when engine coolant temperature is less than 35°F (2°C).

The numbers below refer to the step numbers in the diagnostic procedures.

1 Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2 This step runs the HO2S Heater Tests and initiate the EVAP System Test. Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria. The engine control module considers the engine to be cold if the following conditions are met: ECT less than 86°F (30°C) and ECT and IAT are within 7°F (5°C) of each other at start-up
3 This step runs the EVAP, AIR and the Oxygen Sensor Tests. The EVAP Test begins once the engine coolant reaches a calibrated temperature. The AIR Test, if equipped, begins shortly after Closed Loop and the indicated speed is achieved. The Oxygen Sensor Tests begin once the engine is at operating temperature, in Closed Loop fuel control, and a calibrated amount of time has elapsed.
4 This step is to run the EGR tests. A steady vehicle speed is required in order to maintain a high, stable signal from the MAP sensor.
5 This step runs the Catalyst Tests. This test runs during the idle period immediately following a cruise period that meets a minimum calibrated RPM and time period.
6 Perform the individual system test for any of the systems that do not update to YES.
7 The I/M System Status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . NOTE: Whenever ignition is turned ON, ignition positive voltage is supplied to HO2S heaters. After verifying the enable criteria, turn OFF the ignition for about 5 minutes to allow the sensors to cool before continuing with the test. Once engine is started, DO NOT turn engine OFF for the remaining portion of the set procedure.
Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure that the vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING (COLD START)»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__conditions-for-running-cold-start) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Set vehicle parking brake. Verify the transmission is in Park (A/T) or Neutral (M/T). Start engine and allow engine to idle for 2 minutes. When complete, go to next step.
In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 55 MPH. Maintain this speed without changing throttle position for 8-10 minutes until engine reaches operating temperature. Continue operating under these conditions for additional 6 minutes. When complete, go to next step.
In order for this test to run, the vehicle must operate in the following conditions: The vehicle speed is reduced to 45 MPH with this speed maintained for one additional minute. Four decelerations of 25 seconds each from 45 MPH while the following criteria is maintained: The throttle is closed, no brake application on either manual or automatic transmissions, no clutch actuation (M/T), no manual downshifts, and vehicle speed remains greater than 25 MPH. After each deceleration period, vehicle is returned to 45 MPH under part throttle acceleration and speed is maintained for 15 seconds. When complete, go to next step.
In order for the next group of tests to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 45-55 MPH and maintain this speed for 2 minutes, then decelerate to 0 MPH. With engine idling for 2 minutes, the following criteria should be maintained: Service brake depressed, transmission in Drive (A/T) or Neutral (M/T) with clutch pedal depressed. When complete, go to next step.
With a scan tool, observe the I/M System Status display. Did all of the I/M System Status indicators update to YES? If yes, go to next step. If no, go to the I/M system Set Procedure for the indicated systems.
Using scan tool, observe emission related DTC portion of I/M system status display. Does the scan tool indicate any emission related DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Rough road conditions may prevent some of the tests from running. Extreme high or low ambient temperatures may prevent tests such as HO2S Heater and EVAP system from initiating. If a step is interrupted before completion, perform the remaining portion of the set procedures. Any portion of the set procedure that requires the engine at operating temperature may be repeated. This allows most of the diagnostics to run and the remaining tests can be performed using the individual system Set Procedures.

If vehicle has recently run, start this procedure at step 3 . This will allow the tests that require the engine at operating temperature to run. Using this method allows shorter cool down periods if the tests requiring a cold start do not initiate.

The scan tool can be used to monitor each of the I/M System Status indicators during the I/M Complete system Set Procedure. When all of the indicators for a test step have updated to YES, testing can move on to the next step even if the remaining portion of the test is not complete. For example, step 3 is designed to run the Catalyst Test. The procedure instructs the technician to operate the vehicle in the enable conditions for 6 minutes. If the test updates to YES within 4 minutes, it is not necessary to continue with the enable conditions and testing can advance to the next step.

The following DTCs are required to set system status to YES

Catalyst System

P0420 - Catalyst System Low Efficiency

EGR System

P0401- EGR Flow Insufficient
P0404 - EGR Open Position Performance
P0405 - EGR Position Sensor Circuit - Low Voltage
P1404 - EGR Closed Position Performance

EVAP System

P0440 - EVAP System
P0442 - EVAP System Small Leak Detected
P0446 - EVAP Vent System Performance
P0447 - EVAP Vent Valve Control Circuit - Low Voltage
P1441 - EVAP System Flow During Non-Purge

Oxygen Sensor System

P0133 - HO2S/O2S Slow Response (Sensor 1)
P0140 - HO2S Circuit Insufficient Activity (Sensor 2)
P1133 - HO2S Insufficient Switching (Sensor 1)
P1134 - HO2S Transition Time Ratio (Sensor 1)

Oxygen Sensor Heater System

P0135 - HO2S Heater Performance (Sensor 1)
P0141 - HO2S Heater Performance (Sensor 2)

Diagnose affected DTCs. See DIAGNOSTIC TROUBLE CODE DEFINITIONS .

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. See CONDITIONS FOR RUNNING . Failure to meet the necessary requirements may produce inaccurate test results.

Conditions For Running

Barometric pressure is greater than 65 kPa.
Engine coolant temperature is 203-212°F (95-100°C).
Intake air temperature is 59-167°F (15-75°C).
Engine in closed loop fuel control.
The engine has run for 6-8 minutes off idle in order to initiate the test.
Battery voltage is 10-18 volts.

The numbers below refer to the step numbers in the diagnostic procedures.

1 Perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2 The catalyst test is performed during the idle period immediately following the cruise period.
3 This step identifies a first failure of a type "B" DTC. A DTC only appears on the I/M System Status display when DTC becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M System Status to update to YES. See «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
4 This step helps identify any unique or any unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__conditions-for-running) .
5 The I/M System Status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Ensure the vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__conditions-for-running) . Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start and idle the engine. Important: In order for this test to run, the vehicle must operate in the following conditions: Accelerate at part throttle to 55 MPH. Maintain this speed without changing the throttle position for 5. Decelerate to 0 MPH. Operate engine at idle for 2 minutes while the following criteria is maintained: Service brake depressed and transmission in Drive (A/T). Using scan tool, observe the I/M System Status display. Did the Catalyst system Status update to YES? If yes, go to step 5 . If no, go to next step.
Using scan tool, observe DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Enter DTC in Specific DTC menu on scan tool. Operate vehicle within Conditions for Running DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__conditions-for-running) . Repeat procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. If yes, go next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Using scan tool, observe emission related DTC portion of I/M System Status display. Does scan tool indicate any emission related DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The control module runs a maximum of 6 tests per trip until the Catalyst System Status updates to YES. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the Malfunction Indicator Light (MIL) is requested. The I/M System Status also registers the number of Diagnostic Trouble Codes (DTC).

The first failure of a type "B" DTC does not constitute a final determination of pass or fail, and will not update the I/M System Status to YES. A second trip is required, and all the conditions to run must be met in order for the test to run again. These conditions may include a partial to complete engine cool down.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

If there is an impending failure, the system may require more time to run the diagnostic than was allotted in the set procedure. If the test does not run after numerous attempts and no DTC is set, review the appropriate scan tool data list and the service information for an indication of why the test does not complete. Some tests may abort due to changes in the conditions while the test is running. For example, changes in engine load, such as a cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.

If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the system status updates to YES.

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the EGR system. The test may be used to set I/M System Status indicators to YES. Ensure that vehicle meets the requirements in Conditions for Running DTC before performing this test. Failure to meet necessary requirements may produce inaccurate test results.

Barometric pressure is greater than 65 kPa.
Engine coolant temperature is 176-230°F (80-110°C).
Intake air temperature is greater than 149°F (65°C).

The numbers below refer to the step numbers on the diagnostic procedure.

1 Perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2 The EGR Active Tests are run during a gradual deceleration with a closed throttle. The vehicle speed is required in order to maintain a high, steady MAP signal.
3 This step is to identify a first failure of a type "B" DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M System Status to update to YES. Refer to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
4 This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
5 The I/M System Status only reports on whether or not a diagnostic has run, not the outcome of the test. If any Emission Related DTC sets after the tests are complete, the DTC will require diagnosis.

Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Ensure vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Start and allow engine to idle. Accelerate at part throttle to 45 MPH with this speed maintained for 1 minute. Perform 4 decelerations of 25 seconds each from 45 MPH while the following criteria is maintained: Throttle is closed, no brake application, no manual downshift, vehicle speed remains greater than 25 MPH. After each deceleration period, vehicle is returned to 45 MPH under part throttle acceleration and speed is maintained for 15 seconds. With a scan tool, observe the I/M System Status display. Did the EGR System Status update to YES? If yes, go to step 5 . If no, go to next step.
Using scan tool, observe DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Using scan tool, observe the Not Ran Since Code Cleared display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Repeat the procedure until the scan tool indicates the diagnostic test has run or for any additional required DTCs that have not run. Using scan tool, observe the I/M System Status display. Did the EGR system Status update to YES? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Using scan tool, observe the emission related DTC portion of I/M System Status display. Does the scan tool indicate any emission related DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The control module only runs the EGR Active Tests during a gradual deceleration with a closed throttle and a vehicle speed greater than 25 MPH. Several deceleration cycles may be necessary in order to accumulate a sufficient number of EGR flow samples. The procedure is for a clear, flat road. If the procedure is performed on a road with a slight down hill grade, the test may acquire the necessary sample counters in one or two decel trips. If the test is interrupted during the procedure, completing the test may take more than three deceleration cycles. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the emission related DTC portion of the I/M System Status display will indicate the Malfunction Indicator Light (MIL) is requested. The I/M System Status also registers the number of DTCs.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the system status updates to YES.

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the EVAP system. The test may be used to set the I/M System Status indicators to YES. Service Bay Tests are included on the scan tool for some systems depending upon vehicle make and model. The test is designed to allow the EVAP Diagnostic Tests to run in service bay conditions. Ensure the vehicle meets the requirements listed in Conditions for Running before performing either EVAP system test. Failure to meet the necessary requirements may produce inaccurate test results.

Note. This is for non scan tool Service Bay Test equipped vehicles.

Barometric pressure is greater than 65 kPa.
Engine coolant temperature is less than 158°F (70°C) after engine warm-up.
Fuel level is 1/4-3/4.
Battery voltage is 10.5-16.0 volts.

The numbers below refer to the step numbers in the diagnostic procedures.

1 Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
3 This step determines whether or not the EVAP System Test has passed. If the system is operating correctly, the scan tool indicates that the system has passed and the I/M System Status updates to YES. If the EVAP Service Bay Test aborts because of lost enable conditions, the test can be repeated once the enable criteria is met.
4 A failed DTC during the EVAP Service Bay Test may not appear in the DTC Information display on some vehicles. The Service Bay Test displays an indication of which test failed as a directive to the appropriate service information. Some vehicles will display the test as aborted and the first failure of type "B" DTC appears in the DTC Information.
5 The EVAP System Test usually begins around an ECT of 176°F (80°C). The vehicle should be operated moderately until this temperature is reached. The engine coolant temperature can be monitored using the scan tool.
6 This step identifies a first failure of a type "B" DTC. A DTC only appears on the I/M System Status display when the DTC becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M System Status to update to YES. Refer to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l)
7 This step helps identify any unique or any unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
8 The I/M System Status only reports on whether or not a diagnostic has run, not what the outcome of the test was. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Using a scan tool, select Special Functions. Determine if vehicle is equipped with a Service Bay Test for EVAP System. Is vehicle equipped with EVAP Service Bay Test? If yes, go to next step. If no, go to step 5 .
Ensure vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Following directions on scan tool, perform EVAP Service Bay Test. Did EVAP system pass the Service Bay Test? If yes, go to step 8 . If no, go to next step.
Observe the scan tool Service Bay Test for an indication of why the test did not pass, e.g., failed DTC, test aborted, etc. Refer to the appropriate service information for diagnosis and repair of the condition as necessary. After repairs, «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Ensure that vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Turn OFF all accessories, e.g., A/C, blower fan, etc. Accelerate at part throttle to 45 MPH and maintained speed until engine reaches operating temperature. This may be up to 8-10 minutes depending on the start-up coolant temperature. Continue the operating conditions for an additional 3 minutes after the engine reaches operating temperature, or until the I/M System Status indicator updates to YES. Decelerate to 0 MPH. Operate engine at idle 2 minutes. Did the EVAP System Status update to YES? If yes, go to step 8 . If no, go to next step.
With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Refer to the Inspection/Maintenance (I/M) System DTC Table to determine which DTCs are required to run in order to complete this test. See «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . With a scan tool, observe the Not Ran Since Code Cleared display. Determine which of the DTCs required for a YES status has not run. Enter the DTC number in the Specific DTC menu of the scan tool. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat 4 - 6 for any additional required DTCs that have not run. With a scan tool, observe the I/M System Status display. Did the EVAP System Status update to YES? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
With a scan tool, observe the Emission Related DTC portion of the I/M System Status display. Does the scan tool indicate any Emission Related DTCs set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Extreme high or low ambient temperatures may prevent the EVAP system Tests from initiating. Performing a visual inspection prior to running the EVAP system Set Procedure may prevent having to repeat the test. A loose fuel cap may cause a test to abort or fail and prevent the I/M System Status from updating. A failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.

The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the emission related DTC portion of the I/M System Status display will indicate the Malfunction Indicator Light (MIL) is requested. The I/M System Status also registers the number of DTCs.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the system status updates to YES.

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the HO2S/O2S system. Test may be used to set the I/M System Status to YES. Ensure vehicle meets the requirements listed in Conditions For Running DTC before performing this test. Failure to meet the necessary requirements may produce inaccurate test results.

Engine coolant temperature is more than 176°F (80°C).
Engine operating in closed-loop.
The engine has been running for more than 4 minutes.
Battery voltage is 10-18 volts.

The numbers below refer to the step numbers in the diagnostic procedures.

1 Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2 The oxygen sensor tests begin shortly after the indicated speed is achieved. The engine RPM may be too low in overdrive on manual transmission vehicles. If difficulty is encountered updating the status, operate the vehicle in the recommended gear during the test.
3 This step is to identify a first failure of a type "B" DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M System Status to update to YES. See «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
4 This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
5 The I/M System Status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Ensure the vehicle is within the Conditions for Running. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start and idle engine. Important: In order for this test to run, the vehicle must operate in the following conditions: Accelerate vehicle to 45-55 MPH and operate vehicle within the specified speed for 6 minutes or until the I/M System Status updates to YES. On M/T, either 5 or 6 speed, may require operation in 4th or 5th gear respectively, in order for this test to run. With a scan tool, review the I/M System Status display. Did the HO2S/O2S system Status update to YES? If yes, go to step 5 . If no, go to next step.
Using scan tool, observe DTC Information. If scan tool indicates any failed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If scan tool does not indicate any failed DTCs, go to next step.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within Conditions For Running DTC. Monitor status of DTCs that are necessary to complete the test in the NOT RAN SINCE CODE CLEARED display of scan tool. Repeat this procedure until scan tool indicates the diagnostic test has run. Repeat this step for any additional required DTCs that have not run. Using scan tool, observe I/M System Status display. Did the HO2S/O2S system Status update to YES? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Using scan tool, observe the emission related DTC portion of the I/M System Status display. Does the scan tool indicate any Emission Related DTCs set? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the system status updates to YES.

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for Heated Oxygen Sensor (HO2S) system. The test may be used to set the I/M System Status to YES. Ensure vehicle meets the requirements listed in conditions for running DTC before performing this test.

The Engine Coolant Temperature (ECT) is less than 90°F (32°C).
The Intake Air Temperature (IAT) is less than 90°F (32°C).
The difference between the IAT and the ECT is less than 7°F (5°C).
Battery voltage is 10-18 volts.

The numbers below refer to the step numbers on the diagnostic procedure.

1 Make sure you perform the I/M System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2 Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria. The HO2S Heater tests may not complete when initiated from a cold start and may require running under a load in order to complete the tests.
3 This step is to identify a first failure of a type "B" DTC. A DTC only appears on the I/M System Status display when it becomes a MIL illuminating DTC. This occurs on the second failure of a type "B" DTC. A first failure of a type "B" DTC will not allow the I/M System Status to update to YES. Refer to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
4 This step is to help identify any unique or unusual criteria required to run the diagnostic test in the event the universal set procedure does not. This information is located in the service information under Conditions for Running the DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
5 The I/M System Status only reports on whether or not a diagnostic has run, not the outcome of the test. If any emission related DTC sets after the tests are complete, the DTC will require diagnosis.

Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, go to «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Perform the following: Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure vehicle is within the Conditions For Running DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Set vehicle parking brake. Place transmission in Park (A/T) or Neutral (M/T). Turn off all of accessories (e.g., A/C, blower fan, etc.). Start engine and allow engine to idle. Allow engine to idle for the specified time or until the I/M System Status indicator updates to YES. Did the HO2S Heater system Status update to YES? If yes, go to step 5 . If no, go to next step.
Using scan tool, observe DTC information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go next step. NOTE: Refer to «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) to determine which DTCs are required to run in order to complete this test.
Using scan tool, observe the NOT RAN SINCE CODE CLEARED display. Determine which of the DTCs required for a YES status has not run. Operate vehicle within the Conditions For Running DTC. See «CONDITIONS FOR RUNNING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Monitor status of DTCs that are necessary to complete the test in the NOT RAN SINCE CODE CLEARED display of scan tool. Repeat procedure until scan tool indicates that all the necessary DTC diagnostic tests have run. Using scan tool, observe I/M System Status display. Did the HO2S Heater system Status update to YES? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Using scan tool, observe emission related DTC portion of I/M System Status display. Does the scan tool indicate any emission related DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The HO2S Heater tests will normally run within the 2 minutes allotted in the procedure. If there is an indeterminate condition, the test may take up to 8 minutes on some vehicles before a decision of pass or fail is made. If the test does not update within the allotted period of time, continue operation within the enable conditions until the test updates to YES. If the test does not update to YES, it may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent the HO2S Heater from initiating. The oxygen sensor heaters are operated by the engine control module. The control module has the ability to monitor the current required by the heaters and does this on a continuous basis.

The I/M System Status will update only when an emission related DTC fails the second time, or when all of the tests pass.

If a diagnostic test is difficult to run, observe the I/M System Status display while maintaining the necessary enable conditions until the system status updates to YES.

SUMMARY

If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to appropriate BASIC DIAGNOSTIC PROCEDURES article. If no DTCs are present and a driveability condition exists, proceed to appropriate TROUBLE SHOOTING - NO CODES article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Note. DTCs are retrieved using a Tech 2 scan tool, or other OBD-II compatible scan tool connected to OBD-II 16-pin Data Link Connector (DLC).

DTC	Definition	(1) Type
BXXXX	Body Control System Malfunction	(2)
CXXXX	Chassis Control System Malfunction	(2)
P0030	HO2S Heater Control Circuit (Sensor 1)	B
P0101	MAF Sensor Performance	B
P0102	MAF Sensor Circuit - Low Voltage	B
P0103	MAF Sensor Circuit - High Frequency	B
P0107	MAP Sensor Circuit - Low Voltage	B
P0108	MAP Sensor Circuit - High Voltage	B
P0112	IAT Sensor Circuit - Low Voltage	B
P0113	IAT Sensor Circuit - High Voltage	B
P0116	ECT Sensor Circuit Performance	B
P0117	ECT Sensor Circuit - Low Voltage	B
P0118	ECT Sensor Circuit - High Voltage	B
P0121	TP Sensor Performance	B
P0122	TP Sensor Circuit - Low Voltage	B
P0123	TP Sensor Circuit - High Voltage	B
P0125	ECT Excessive Time To Enter Closed Loop	B
P0128	Engine Coolant Thermostat	B
P0130	HO2S Circuit (Sensor 1)	B
P0131	HO2S Circuit - Low Voltage (Bank 1; Sensor 1)	B
P0132	HO2S Circuit - High Voltage	B
P0133	HO2S Slow Response	B
P0134	HO2S Circuit Insufficient Activity	B
P0135	HO2S Heater Performance	B
P0137	HO2S Circuit - Low Voltage	B
P0138	HO2S Circuit - High Voltage	B
P0140	HO2S Circuit Insufficient Activity (Bank 1; Sensor 2)	B
P0141	HO2S Heater Performance (Bank 1; Sensor 2)	B
P0171	Lean Fuel Trim System (Bank 1)	B
P0172	Rich Fuel Trim System (Bank 1)	B
P0201-P0206	Injector Control Circuit	B
P0218 (3)	Transmission Over Temperature Condition	B
P0230	Fuel Pump Primary Circuit	C
P0300	Engine Misfire Detected	B
P0325	KS Module Circuit	B
P0327	KS Circuit - Low Voltage (Bank 1)	B
P0336	CKP Sensor Circuit Performance	B
P0341	CMP Sensor Circuit Performance	B
P0401	EGR System	A
P0403	EGR Solenoid Control Circuit	B
P0404	EGR System	B
P0405	EGR Sensor Circuit - Low Voltage	B
P0420	TWC System Low Efficiency (Bank 1)	B
P0440	EVAP System	B
P0442	EVAP System - Leak Detected	A
P0443	EVAP Purge Solenoid Control Circuit	B
P0446	EVAP Canister Vent Blocked	B
P0449	EVAP Canister Vent Solenoid Control Circuit	B
P0452	Fuel Tank Pressure Sensor Circuit - Low Voltage	B
P0453	Fuel Tank Pressure Sensor Circuit - High Voltage	B
P0462 (4)	Fuel Level Circuit Low Voltage	C
P0463 (4)	Fuel Level Circuit - High Voltage	C
P0480 (5)	Cooling Fan No. 1 Control Circuit	B
P0481 (5)	Cooling Fan No. 2 Control Circuit	B
P0502 (3)	VSS Circuit Low Input	B
P0503 (3)	VSS Circuit Performance	B
P0506	Idle Speed - Low	B
P0507	Idle Speed - High	B
P0530 (6)	A/C Refrigerant Pressure Sensor Circuit	C
P0560 (7)	System Voltage	C
P0601-P0607, P1600, P1621, P1627, P1680, P1681 Or P1683	Control Module Read Only Memory	(8) A
P0620 (7)	Generator Control Circuit	C
P0650	MIL Control Circuit	B
P0711 (3)	TFT Sensor Out Of Range	C
P0712 (3)	TFT Sensor Circuit - Low Voltage	C
P0713 (3)	TFT Sensor Circuit - High Voltage	C
P0716 (3)	Input Turbine Speed Sensor Circuit Performance	B
P0717 (3)	Input Turbine Speed Sensor Circuit - No Signal	B
P0719 (3)	Brake Switch 2 Circuit - Low Voltage	C
P0724 (3)	Brake Switch 2 Circuit - High Voltage	C
P0730 (3)	Incorrect Gear Ratio	C
P0741 (3)	TCC Circuit Performance Or Stuck Off	B
P0742 (3)	TCC Circuit Stuck On	A
P0748 (3)	Pressure Control Solenoid Electrical	C
P0751 (3)	Shift Solenoid 1 Performance Or Stuck Off	B
P0752 (3)	1-2 Shift Solenoid Stuck On	B
P0753 (3)	Shift Solenoid 1 Electrical	B
P0756 (3)	Shift Solenoid 2 Performance Or Stuck Off	A
P0757 (3)	2-3 Shift Solenoid Stuck On	A
P0758 (3)	Shift Solenoid 2 Electrical	A
P1106	MAP Sensor Circuit Intermittent High Voltage	C
P1107	MAP Sensor Circuit Intermittent Low Voltage	C
P1111	IAT Sensor Circuit Intermittent High Voltage	C
P1112	IAT Sensor Circuit Intermittent Low Voltage	C
P1114	ECT Sensor Circuit Intermittent Low Voltage	C
P1115	ECT Sensor Circuit Intermittent High Voltage	C
P1121	TP Sensor Circuit Intermittent High Voltage	C
P1122	TP Sensor Circuit Intermittent Low Voltage	C
P1133	HO2S Insufficient Switching (Bank 1; Sensor 1)	B
P1134	HO2S Transition Time Ratio (Bank 1; Sensor 1)	B
P1189 (4)	Engine Oil Pressure Switch Circuit	C
P1336	Crankshaft Position System Variation Not Learned	A
P1351	IC Circuit High Voltage	B
P1352	IC Output High/Pulse Detected	B
P1361	IC Circuit Low Voltage	B
P1362	IC Cylinder No. 2 Not Toggling After Enable	B
P1374	3X Reference Circuit	B
P1380	EBTCM DTC Detected Rough Road Data Unusable	C
P1381	Misfire Detected No EBTCM/PCM Serial Data	C
P1404	EGR System (Valve No. 2)	B
P1441	EVAP System Flow During Non-Purge	B
P1546 (6)	A/C Clutch Status Circuit - Low Voltage	C
P1554 (9)	Cruise Engaged Circuit - High Voltage	C
P1585 (9)	Cruise Inhibit Control Circuit	C
P1626 (10)	Theft Deterrent System Fuel Enable Circuit	C
P1630 (10)	Theft Deterrent System - PCM In Learn Mode	C
P1631 (10)	Theft Deterrent System - Password Incorrect	C
P1635	5-Volt Reference Low	B
P1639	5-Volt Reference 2 Circuit	B
P1640	Driver 1 Input - High Voltage	C
P1650	Driver 2 Input - High Voltage	C
P1660	Cooling Fans Control Circuit	C
P1670	Output Driver Module No. 4	C
P1810 (3)	Pressure Switch Manifold	B
P1811 (3)	Maximum Adapt & Long Shift	C
P1814 (3)	Torque Converter Overstressed	C
P1819 (3)	Internal Mode Switch - No Start/Wrong Range	C
P1820 (3)	Internal Mode Switch Circuit "A" - Low	C
P1822 (3)	Internal Mode Switch Circuit "B" - High	C
P1823 (3)	Internal Mode Switch Circuit "P" - Low	C
P1825 (3)	Internal Mode Switch - Illegal Range	C
P1826 (3)	Internal Mode Switch Circuit "C" - High	C
P1860 (3)	TCC PWM Solenoid Circuit	B
P1887 (3)	TCC Release Switch Circuit	B
(1) See appropriate CODE TYPES under ON-BOARD DIAGNOSTICS in SELF-DIAGNOSTIC SYSTEM. (2) For a complete listing of body and chassis codes, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. (3) See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. (4) See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. (5) See COOLING SYSTEMS article in ENGINES. (6) See appropriate A/C-HEATER SYSTEMS article in appropriate AIR CONDITIONING & HEATING. (7) See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS. (8) DTC P1683 is a code type "B". (9) See appropriate CRUISE CONTROL article in ACCESSORIES & EQUIPMENT. (10) See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.

(1)	See appropriate CODE TYPES under ON-BOARD DIAGNOSTICS in SELF-DIAGNOSTIC SYSTEM.

(2)	For a complete listing of body and chassis codes, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.

(3)	See appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS.

(4)	See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT.

(5)	See COOLING SYSTEMS article in ENGINES.

(6)	See appropriate A/C-HEATER SYSTEMS article in appropriate AIR CONDITIONING & HEATING.

(7)	See appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.

(8)	DTC P1683 is a code type "B".

(9)	See appropriate CRUISE CONTROL article in ACCESSORIES & EQUIPMENT.

(10)	See appropriate ANTI-THEFT SYSTEMS article in ACCESSORIES & EQUIPMENT.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Scheme 2

Scheme 2: COMPONENT LOCATIONS

Scheme 3

Scheme 4

Scheme 5

Scheme 6

Scheme 7

Scheme 8

Scheme 8: CONNECTOR IDENTIFICATION

Scheme 9

Scheme 10

Scheme 11

Scheme 12

Scheme 13

Scheme 14

Scheme 15

Scheme 16

Scheme 17

Scheme 18

Scheme 19

Scheme 20

Scheme 21

Scheme 22

Scheme 23

Scheme 24

Scheme 25

Scheme 26

Scheme 27

Scheme 28

Scheme 29

Scheme 30

Scheme 31

Scheme 32

Scheme 33

Scheme 34

Scheme 35

Scheme 36

Scheme 37

MIL INOPERATIVE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Circuit Description

There should be a steady Malfunction Indicator Light (MIL) with the ignition ON and the engine OFF. Ignition feed voltage is supplied directly to the MIL. The Powertrain Control Module (PCM) turns the MIL ON by grounding the MIL control circuit. No MIL with the key ON, engine not running suggests an open in the battery positive and ignition positive voltage feed fuses and circuits.

MIL Operation

MIL is located on instrument panel and is displayed as CHECK ENGINE light.

MIL Function

The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
The MIL illuminates during a bulb test and a system test.
A DTC will be stored if a MIL is requested by the diagnostic.

MIL Illumination

The MIL will illuminate with ignition ON and the engine not running.
The MIL will turn OFF when the engine is started.
The MIL will remain ON if the self-diagnostic system has detected a malfunction.
The MIL may turn OFF if the malfunction is not present.
If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.

Perform the Diagnostic System Check - Engine Controls, when the following conditions are present

The MIL does not turn ON when the ignition switch is turned to the RUN position. See above for MIL operation.
The MIL remains ON while the engine is running.
The MIL is flashing while the engine is running.
A driveability symptom is determined.

The numbers below refer to the step numbers on the diagnostic procedures.

3 This step determines if the condition is with the MIL control circuit or the PCM.
4 This step determines if a voltage is constantly being applied to the control circuit.

Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.
Attempt to start engine. Does engine start? If yes, go to next step. If no, go to step 9 .
Inspect the fuse supplying voltage to the MIL. Is fuse open? If yes, go to step 7 . If no, go to next step.
Turn OFF ignition. Disconnect PCM connector containing the MIL control circuit. Turn ON ignition, with engine OFF. Probe MIL control circuit in PCM harness connector with a fused jumper wire connected to ground. Is MIL ON? If yes, go to step 16 . If no, go to next step.
Turn ignition off. Remove Instrument Panel (IP). Probe the MIL ignition positive voltage circuit at the IP harness connector with a test light connected to a good ground. Is test light illuminated? If yes, go to next step. If no, go to step 8 .
Test the MIL control circuit for an open or high resistance and repair as necessary. Did you find and correct the condition? If yes, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 14 .
Repair the short to ground in the MIL ignition positive voltage circuit. After repairs, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.
Repair the open in the MIL ignition positive voltage circuit. After repairs, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.
Inspect PCM fuse and ignition 1 main fuse. Is one or both of the fuses open? If yes, go to step 12 . If no, go to next step.
Turn OFF ignition. Disconnect PCM. Turn ON ignition, with engine OFF. Connect a test light between PCM ignition positive voltage circuits and a good ground. Does the test light illuminate while probing all PCM ignition positive voltage circuits? If yes, go to next step. If no, go to next step 12 .
Connect a test light from PCM battery positive voltage circuit and good ground. Does the test light illuminate? If yes, go to step 13 . If no, go to next step.
Locate and repair open or short to ground in PCM ignition feed circuits or PCM battery positive voltage circuit. After repairs, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.
Inspect for a poor PCM ground or a poor PCM ground connection. Repair the condition as necessary. Did you find and correct the condition? If yes, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 15 .
Inspect for poor connections at the IP and repair as necessary. Did you find and correct the condition? If yes, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 16 .
Inspect for poor connections at PCM and repair as necessary. Did you find and correct the condition? If yes, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 17 .
Replace the IP. When complete, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.
Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. When complete, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.

Inspect for the following conditions

If engine runs okay, inspect for a malfunctioning MIL, an open in MIL control circuit, or an open in the instrument cluster ignition feed.
If the engine cranks but will not run, inspect for an open PCM ignition or battery feed or a faulty PCM to engine ground.
PCM and engine grounds for clean and secure connections

MIL ON STEADY

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The diagnostic system check - engine controls must be the starting point for any driveability complaint diagnosis. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. Perform a careful visual and physical inspection of the Powertrain Control Module (PCM) and engine grounds for being clean and tight. Diagnostic system check - engine controls is an organized approach to identifying a condition created by an electronic engine control system malfunction.

The Powertrain Control Module (PCM) controls the Malfunction Indicator Light (MIL) by providing a ground path through the MIL control circuit to turn ON the MIL. When the ignition is turned ON, the MIL will remain on until the engine is running, if no Diagnostic Trouble Codes (DTC) are stored. If MIL is illuminated, then engine stalls, the MIL will remain illuminated so long as ignition is ON.

MIL is located on the instrument panel and is displayed as CHECK ENGINE light.

MIL Function

The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
The MIL illuminates during a bulb test and a system test.
A DTC will be stored if a MIL is requested by the diagnostic.

MIL Illumination

The MIL will illuminate with ignition ON and the engine not running.
The MIL will turn OFF when the engine is started.
The MIL will remain ON if the self-diagnostic system has detected a malfunction.
The MIL may turn OFF if the malfunction is not present.
If the MIL is illuminated and then the engine stalls, the MIL will remain illuminated so long as the ignition switch is ON.
If the MIL is not illuminated and the engine stalls, the MIL will not illuminate until the ignition switch is cycled OFF, then ON.

Perform the Diagnostic System Check - Engine Controls, when the following conditions are present

The MIL does not turn ON when the ignition switch is turned to the RUN position. See above for MIL operation.
The MIL remains ON while the engine is running.
The MIL is flashing while the engine is running.
A driveability symptom is determined.

The number below refers to the step number on the diagnostic procedures.

5 Using a test light connected to battery positive voltage, probe the MIL control circuit at PCM.

Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.
With a scan tool observe the DTCs. Are any DTCs set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If yes, go to next step.
Turn ignition off. Observe the MIL on the Instrument Panel (IP) cluster. Is MIL ON? If yes, go to step 7 . If no, go to next step.
Install a scan tool. Command MIL ON and OFF several times while monitoring the IP cluster. Does the MIL turn ON and OFF when commanded? If yes, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to step 6 .
Repair MIL control circuit for a short to ground. After repairs, go to step 7 .
Repair MIL control circuit for a short to voltage. After repairs, go to next step.
Install a scan tool. Command MIL ON and OFF several times while monitoring the IP cluster. Does the MIL turn OFF when commanded? If yes, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 2 .

If the problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DIAGNOSTIC TESTS

Note. Before clearing DTCs, perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. Record FREEZE FRAME and FAILURE RECORDS for reference during testing. Data will be erased when DTCs are cleared.

Note. If PCM is replaced, NEW PCM must be programmed. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE under PROGRAMMING.

DTC P0030: HO2S HEATER CONTROL CIRCUIT (SENSOR 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and then provide an accurate voltage signal. The PCM controls the HO2S 1 heater low control circuit with a low side driver. The HO2S 1 heater diagnostic monitors the current draw through the HO2S 1 low side driver when the engine is running. This DTC will set if the current level exceeds a calibrated amount.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage, heater low control, and low reference loop circuit.

Conditions For Running DTC

The engine is running.

Conditions For Setting DTC

The PCM detects that the heater control circuit current is greater than the capacity of the PCM internal driver for more than 20 seconds.

Action Taken When DTC Sets

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

Conditions For Clearing MIL/DTC

The PCM turns OFF the MIL lamp after 3 consecutive ignition cycles that the diagnostic runs and passes. A current, DTC last test fails, clears when the diagnostic runs and passes. A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic. A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 Inspect the heater current with the engine at operating temperature, and allow time for the heater current to stabilize. The HO2S 1 heater current is initially higher until the sensor reaches full operating temperature.
4 A DTC fail in this step verifies the problem is present with the HO2S 1 disconnected.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Monitor the HO2S 1 Heater Current parameter on a scan tool. Allow the current to stabilize. Is the HO2S 1 Heater Current within 0.25-0.85 A? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__conditions-for-running-dtc) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1. Start the engine. Allow the engine to idle at operating temperature. Monitor the scan tool for at least 30 seconds. Does the DTC fail this ignition? If yes, go to next step. If no, go to step 6 .
Test the HO2S 1 heater low control circuit for a short to voltage. If yes, go to step 10 . If no, go to step 7 .
Inspect for poor connections at the harness connector of the HO2S 1. Did you find and correct the condition? If yes, go to step 10 . If no, go to step 8 .
Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 10 . If no, go to step 9 .
Replace the HO2S 1. After replacing sensor, go to step 10 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__conditions-for-running-dtc) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0101: MAF SENSOR PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering the engine. The Powertrain Control Module (PCM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has an ignition 1 voltage circuit, a ground circuit, and a signal circuit.

The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. The frequency varies within a range of around 2000 Hertz at idle to about 10,000 Hertz at maximum engine load. The PCM uses the following sensor inputs in order to calculate a predicted MAF value

Barometric Pressure (BARO) at key ON.
Manifold Absolute Pressure (MAP).
Engine Coolant Temperature (ECT).
Intake Air Temperature (IAT).
Throttle Position (TP).
Engine speed (RPM).

The PCM compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison determines if the signal is stuck based on a lack of variation, or is too low or too high for a given operating condition. DTC P0101 sets if the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value.

DTCs P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0401, P0404, P0405, P0440, P0442, P0446, P1404, and P1441 are not set.
The engine is running.
The ignition 1 signal is 9-18 volts.
The TP sensor angle is less than 25 percent.
The change in the TP sensor angle is less than 1.5 percent.
The MAP sensor is less than 63 kPa.
The change in the MAP sensor is less than 3 kPa.
The above conditions are met for 5 seconds.

The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 This step determines if the MAP sensor voltage is within the proper range at idle.
5 This step determines if the MAP sensor responds properly to the change in manifold pressure.
6 This step determines if the Throttle Position (TP) sensor is operating properly.
7 This step determines if any mechanical faults have caused this DTC to set.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Start the engine. Monitor the Diagnostic Trouble Code (DTC) Information with the scan tool. Does the scan tool display any other DTCs set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. If yes, see «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Allow the engine to reach operating temperature. Observe the MAP sensor voltage with a scan tool. Is the MAP sensor voltage within 0.8-4.0 volts? If yes, go to next step. If no, diagnose MAP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
Idle the engine. Observe the MAP sensor kPa with a scan tool. Increase the engine speed slowly to 3000 RPM and then back to idle. Does the MAP sensor kPa change smoothly and gradually through the specified range of the test? If yes, go to next step. If no, diagnose MAP sensor. See ENGINE SENSORS & SWITCHES in appropriate SYSTEM & COMPONENT TESTING article.
Turn ignition off. Turn ignition on, with engine off. Observe the TP sensor angle from closed throttle to wide open throttle. Depress completely and then release the accelerator pedal. Does the scan tool indicate that the TP sensor angle changed smoothly and completely through the specified range of 0-100 percent? If yes, go to next step. If no, go to «DTC P0121: THROTTLE POSITION SENSOR PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0121-throttle-position-sensor-performance) .
Inspect for a restricted air intake duct, collapsed air intake duct, dirty air filter element, or a deteriorating air filter element. Check for any object blocking the air inlet screen of MAF sensor, any debris on the sensing elements of MAF sensor, vacuum leak downstream of MAF sensor, a poor vacuum connection at MAP sensor, a skewed or stuck ECT sensor. Check for high resistance in ground circuit of the ECT sensor or a restricted exhaust system. Did you find and correct the condition? If yes, go to step 10 . If no, go to next step.
Test for an intermittent and for a poor connection at the MAF sensor. Did you find and correct the condition? If yes, go to step 10 . If no, go to next step.
Replace the MAF sensor. After replacing sensor, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

An incorrectly routed harness. Inspect the MAF sensor harness in order to verify that the harness is not routed too close to the following components: The secondary ignition wires or coils, solenoids, relays or motors.
A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leaks downstream of the MAF sensor.
A wide open throttle acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 4-7 g/s at idle to 130 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
A skewed or stuck TP sensor.
A skewed or stuck ECT sensor.
The barometric pressure that is used in order to calculate the predicted mass air flow value is initially based on the MAP sensor at key ON. When the engine is running the MAP sensor value is continually updated near Wide Open Throttle (WOT). A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate. The value shown for the MAP sensor display varies with the altitude. With the ignition ON and the engine OFF, 103 kPa is the approximate value near sea level. This value will decrease by approximately 3 kPa for every 305 meters (1000 feet) of altitude.
High resistance on the ground circuit of the MAP sensor can cause this DTC to set.
Any loss of vacuum to the MAP sensor can cause this DTC to set.
High resistance on the ground circuit of the ECT sensor can cause this DTC to set.

Problem could also be caused by aftermarket accessories. If the condition is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0102: MAF SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering the engine. The Powertrain Control Module (PCM) uses the MAF sensor signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has the following circuits: An ignition 1 voltage circuit, ground circuit and a signal circuit.

The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. The frequency varies within a range of around 2000 Hertz at idle to about 10,000 Hertz at maximum engine load. DTC P0102 sets if the PCM detects a frequency signal lower than the possible range of a properly operating MAF sensor.

The engine is running.
The Idle Air Control (IAC) position is more than 2 counts.
The ignition 1 signal is more than 8 volts.
The above conditions are met for more than 0.5 second.

The PCM detects that the MAF sensor frequency signal is less than 1200 Hz.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 This step determines if any mechanical faults have caused this DTC to set.
9 This step verifies the signal circuit from the MAF sensor electrical connector to the PCM. A voltage reading of less than 4 volts or greater than 6 volts indicates a malfunction in the wiring or a poor connection.
10 This step tests the signal circuit of the MAF sensor for a short to another 5-volt reference circuit.
16 This step verifies that the signal circuit is not shorted to any other PCM circuit.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Start the engine. Observe the MAF sensor frequency with a scan tool. Is the MAF sensor frequency less than 1200 Hz? If yes, go to step 4 . If no, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or until the DTC diagnostic has run. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Observe the MAF sensor frequency with a scan tool. Move the harness and the connector of the MAF sensor. Does the movement of the harness or the connector affect the MAF sensor frequency? If yes, go to step 25 . If no, go to next step.
Turn ignition off. Inspect for a restricted air intake duct, collapsed air intake duct, dirty air filter element, or deteriorating air filter element. Check for objects blocking the air inlet screen of MAF sensor, or debris on the sensing elements of MAF sensor. Check for a restricted exhaust system, any vacuum leak downstream of MAF sensor or a MAF sensor that is installed backwards. Did you find and correct the condition? If yes, go to step 30 . If no, go to next step.
Inspect the fuse in the ignition 1 voltage circuit of the MAF sensor. Is the fuse open? If yes, go to step 12 . If no, go to next step.
Disconnect the harness connector of the MAF sensor. Turn ignition on, with engine off. Connect a test light between the ignition 1 voltage circuit of the MAF sensor and a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step 18 .
Connect a test light between the ignition 1 voltage circuit of the MAF sensor and the ground circuit of the MAF sensor. Does the test light illuminate? If yes, go to next step. If no, go to step 19 .
Measure the voltage from the signal circuit of the MAF sensor to a good ground. Is the voltage about 5 volts? If yes, go to next step. If no, go to step 11 .
Connect a 3-amp fused jumper wire between the signal circuit of the MAF sensor and a good ground. Start the engine. Do any additional DTCs set? If yes, go to step 23 . If no, go to step 26 .
Is the voltage less than 4.5 volts? If yes, go to step 13 . If no, go to step 15 .
Test for continuity between the ignition 1 voltage circuit of the MAF sensor and ground. Does the Digital Multimeter (DMM) indicate continuity? If yes, go to step 17 . If no, go to step 26 .
Turn ignition off. Disconnect the PCM. Test the signal circuit between the PCM and the MAF sensor for high resistance or open circuit. Does the DMM indicate continuity? If yes, go to next step. If no, go to step 20 .
Test for continuity from the signal circuit of the MAF sensor to ground. Does the DMM indicate continuity? If yes, go to step 21 . If no, go to step 16 .
Turn ignition off. Disconnect the PCM. Turn ignition on, with engine off. Measure the voltage from the signal circuit of the MAF sensor to a good ground. Is the voltage about 0 volts? If yes, go to next step. If no, go to step 22 .
Test for continuity at the harness connector of the PCM from the signal circuit of the MAF sensor to all other circuits at both PCM connectors. Does the DMM indicate continuity between any other circuit? If yes, go to step 24 . If no, go to step 27 .
Repair the short to ground in the ignition 1 voltage circuit of the MAF sensor. Replace the fuse if necessary. After repairs, go to step 30 .
Repair the open in the ignition 1 voltage circuit of the MAF sensor. After repairs, go to step 30 .
Repair the high resistance or open in the ground circuit of the MAF sensor. After repairs, go to step 30 .
Repair the high resistance or open in the signal circuit of the MAF sensor. After repairs, go to step 30 .
Repair the short to ground in the signal circuit of the MAF sensor. After repairs, go to step 30 .
Repair the short to voltage in the signal circuit of the MAF sensor. After repairs, go to step 30 .
Repair the short between the signal circuit of the MAF sensor and the circuit for which the DTC set. After repairs, go to step 30 .
Repair the circuits that are shorted together. After repairs, go to step 30 .
Repair the harness or the connections as needed. After repairs, go to step 30 .
Test for an intermittent and for a poor connection at the MAF sensor. Did you find and correct the condition? If yes, go to step 30 . If no, go to step 28 .
Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step 30 . If no, go to step 29 .
Replace the MAF sensor. After replacing sensor, go to step 30 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to step 10 .
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR SETTING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

An incorrectly routed harness. Inspect the MAF sensor harness in order to verify that the harness is not routed too close to the following components: The secondary ignition wires or coils, solenoids, relays or any motors.
A low minimum air rate through the sensor bore may cause this DTC to set at idle or during deceleration. Inspect for any vacuum leak downstream of the MAF sensor.
A wide open throttle acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 4-7 g/s at idle to 130 g/s or more at the time of the 1-2 shift. If the increase is not observed, inspect for a restriction in the induction system or the exhaust system.
A resistance of 20 ohms or more on the ground circuit of the MAF sensor can cause this DTC to set.

Problem can be caused by aftermarket accessories. An intermittent malfunction may be caused by a fault in the MAF sensor circuit. Inspect the wiring harness and components for an intermittent condition. Refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0103: MAF SENSOR CIRCUIT - HIGH FREQUENCY

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Mass Airflow (MAF) sensor is an airflow meter that measures the amount of air entering the engine. The Powertrain Control Module (PCM) uses the MAF sensor frequency signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has the following: An ignition 1 voltage circuit, ground circuit and signal circuit.

The PCM applies a voltage to the sensor on the signal circuit. The sensor uses the voltage in order to produce a frequency based on inlet air flow through the sensor bore. The frequency varies within a range of around 2000 Hertz at idle to about 10,000 Hertz at maximum engine load. DTC P0103 sets if the PCM detects a frequency signal higher than the possible range of a properly operating sensor.

The engine is running.
The Idle Air Control (IAC) position is more than 2 counts.
The ignition 1 signal is more than 8 volts.
The above conditions are met for more than 0.5 second.

The PCM detects that the MAF sensor frequency signal is more than 11,500 Hz.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

3 This step tests for Electromagnetic Interference (EMI) on the signal circuit of the MAF sensor. A frequency reading with the MAF sensor disconnected indicates an EMI related fault or a poor connection. Disconnecting the MAF sensor may set additional related DTCs.
4 This step eliminates any conditions which can cause a DTC to set with a properly operating MAF sensor.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the harness connector of the MAF sensor. Start the engine. Observe the MAF sensor frequency with a scan tool. Does the scan tool display 0 Hz? If yes, go to step 5 . If no, go to next step.
Inspect the harness of the MAF sensor for incorrect routing that is too close to the secondary ignition wires or coils, any solenoids, relays or motors. Did you find and correct the condition? If yes, go to step 9 . If no, go to step. 6 .
Test for an intermittent and for a poor connection at the MAF sensor. Did you find and correct the condition? If yes, go to step 9 . If no, go to step 7 .
Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step 9 . If no, go to step 8 .
Replace MAF sensor. After replacing sensor, go to step 9 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Any water that enters the air intake system that reaches the MAF sensor could cause this DTC to set. The water rapidly cools the hot sensing elements in the sensor causing a false indication of excessive air flow. Inspect the following areas for evidence of water intrusion: The air induction system and Secondary Air Injection (AIR) system.
A poor connection in the ignition 1 voltage circuit of the MAF sensor can cause a DTC P0103 to set.

Problem could be caused by aftermarket accessories. Repair as necessary. If the condition is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0107: MAP SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits: 5-volt reference circuit, low reference circuit and sensor signal circuit.

The Powertrain Control Module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit. The PCM also provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the MAP sensor signal circuit which is relative to the pressure changes in the manifold. The PCM should detect a low signal voltage at a low MAP, such as during an idle or a deceleration. The PCM should detect a high signal voltage at a high MAP, such as the ignition is ON, with the engine OFF, or at a Wide Open Throttle (WOT). The MAP sensor is also used in order to determine the Barometric Pressure (BARO). This occurs when the ignition switch is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range.

If PCM detects a MAP sensor signal voltage that is excessively low, this DTC will set.

DTCs P0121, P0122, or P0123 are not set.
The engine is running.
The throttle angle is more than 0 percent, if the engine speed is less than 1000 RPM.

The MAP sensor signal voltage is less than 0.1 volt (12 kPa) for 3 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The MAP sensor 5-volt reference circuit is shared with other sensors. If DTC P1635 is set, this indicates that the 5-volt reference circuit is shorted to ground and should be diagnosed first. The short may be on another sensor 5-volt reference circuit.
4 Operate the vehicle within the same conditions as when the DTC failed. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in locating an intermittent condition.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start the engine. Does the scan tool indicate that DTC P1635 is current? If yes, go to «DTC P1635: 5-VOLT REFERENCE LOW»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p1635-5-volt-reference-low) . If no, go to next step.
Observe the MAP sensor voltage with a scan tool. Does the voltage measure less than 0.1 volt? If yes, go to step 5 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the MAP sensor electrical connector. Connect a test light to a known-good ground. Probe the 5-volt reference circuit of the MAP sensor with the test light. Perform a voltage drop test across the test light with a Digital Multimeter (DMM). Turn ignition on, with engine off. Does the voltage measure more than 4.4 volts? If yes, go to next step. If no, go to step 7 .
Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor. Does the scan tool indicate that the MAP sensor voltage is about 5 volts? If yes, go to step 9 . If no, go to step 8 .
Test the 5-volt reference circuit of the MAP sensor for high resistance or an open. Did you find and correct the condition? If yes, go to 13 . If no, go to step 10 .
Test the signal circuit of the MAP sensor for a short to ground or an open. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 10 .
Inspect for poor connections at the harness connector of the MAP sensor. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 11 .
Inspect for poor connections at the Powertrain Control Module (PCM). Did you find and correct the condition? If yes, go to step 13 . If no, go to step 12 .
Replace the MAP sensor. After replacing sensor, go to step 13 . If no, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If any DTCs are stored, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0108: MAP SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure which gives an indication of the engine load. The MAP sensor has the following circuits, a 5-volt reference circuit, low reference circuit and a signal circuit.

The PCM supplies 5 volts to the MAP sensor on the 5-volt reference circuit and provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to the pressure changes in the manifold. With low manifold absolute pressure such as during idle or deceleration, the PCM should detect a low MAP sensor signal voltage. With high manifold absolute pressure such as ignition ON, with the engine OFF or Wide Open Throttle (WOT), the PCM should detect a high MAP sensor signal voltage. Certain vehicle models will also use the MAP sensor in order to calculate the Barometric Pressure (BARO) when the ignition is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 will set.

DTCs P0121, P0122, or P0123 are not set.
The engine has been running for a length of time that is determined by the start-up coolant temperature. The length of time ranges from 2 minutes at less than -22°F (-30°C) to 1 second at more than 86°F (-30°C).
The throttle angle is less than 2 percent when the engine speed is less than 3000 RPM or throttle angle is less than 30 percent when engine speed is more than 3000 RPM.

The MAP sensor signal voltage is more than 4.3 volts for 3 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The MAP sensor 5-volt reference circuit is shared with other sensors. If DTC P1635 is set, this indicates that the 5-volt reference circuit is either shorted to ground or shorted to voltage and should be diagnosed first. The short may be on another sensor 5-volt reference circuit.
4 Operate the vehicle within the same conditions as when the DTC failed. If you cannot duplicate the DTC, the information included in the Freeze Frame/Failure Records data can aid in locating an intermittent condition.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start the engine. Does the scan tool indicate that DTC P1635 is current? If yes, go to «DTC P1635: 5-VOLT REFERENCE LOW»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p1635-5-volt-reference-low) . If no, go to next step.
Does the scan tool indicate that the MAP sensor voltage is more than 4.3 volts? If yes, go to step 5 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Inspect the MAP sensor and the vacuum source for vacuum line disconnected from MAP sensor, vacuum line pinched or cut, or blocked vacuum port. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Disconnect the MAP sensor electrical connector. Turn ignition on, with engine off. Does the scan tool indicate that the MAP sensor voltage is less than 0.1 volt? If yes, go to next step. If no, go to step 8 .
Disconnect Engine Coolant Temperature (ECT) sensor harness connector. ECT sensor is located near thermostat housing. Connect a test light to B+. Probe the low reference circuit of the MAP sensor with the test light. Does the test light illuminate? If yes, go to step 10 . If no, go to step 9 .
Test the signal circuit of the MAP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Test the low reference circuit of the MAP sensor for high resistance or for open. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Inspect for poor connections at the MAP sensor. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the PCM. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the MAP sensor. After replacing sensor, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use a scan tool to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Inspect the MAP sensor vacuum source for leaks, for restrictions, or for poor connections.

An intermittent malfunction may be caused by a fault in the MAP sensor circuits. Inspect the wiring harness and components for an intermittent condition. Refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Intake Air Temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT signal circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an excessively low IAT signal voltage, indicating a high temperature, DTC P0112 sets.

DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0125, P0128, P0502, or P0503 are not set.
The engine run time is more than 10 seconds.
The vehicle speed sensor indicates that vehicle speed is more than 25 MPH.

The IAT is more than 253°F (123°C) for 20 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. Observe the IAT sensor temperature with a scan tool. Is the IAT sensor temperature more than 262°F (128°C)? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC reset? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect IAT sensor. IAT sensor is mounted on air intake hose. Turn ignition on, with engine off. Observe the IAT sensor temperature with a scan tool. Is the IAT sensor temperature less than -38°F (-39°C)? If yes, go to step 6 . If no, go to next step.
Test the signal circuit of the IAT sensor for a short to ground or a short to IAT low reference circuit and repair as necessary. Did you find and correct the condition? If yes, go to step 9 . If no, go to step 7 .
Replace IAT sensor. After replacing sensor, go to step 9 .
Turn ignition off. Disconnect the PCM. Inspect for poor connection at the PCM harness connector. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

When the vehicle is at ambient temperature the IAT sensor and Engine Coolant Temperature (ECT) sensor temperatures should be relatively close to each other. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.

An intermittent malfunction may be caused by a fault in the IAT sensor circuit. Inspect the wiring harness and components for an intermittent condition. Refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0113: IAT SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Intake Air Temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT signal circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an excessively high IAT signal voltage, indicating a low temperature, DTC P0113 sets.

DTCs P0116, P0117, P0118, P0125, P0128, P0502, or P0503 are not set.
The engine run time is more than 180 seconds.
The Vehicle Speed Sensor (VSS) indicates that vehicle speed is less than 35 MPH.
The Mass Airflow (MAF) is less than 12 g/s.
The Engine Coolant Temperature (ECT) is more than 140°F (60°C).

The Intake Air Temperature (IAT) is less than -38°F (-39°C) for more than 3 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

6 This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. Observe the IAT sensor temperature with a scan tool. Is the IAT sensor temperature less than -36°F (-38°C)? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC reset? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the IAT sensor. Connect a Digital Multimeter (DMM) between the signal circuit and the low reference circuit of the IAT sensor harness. Turn ON the ignition. Does the DMM voltage measure more than 5 volts? If yes, go to step 6 . If no, go to next step.
Test the IAT sensor signal circuit for a short to voltage. Repair as necessary. Did you find and correct the condition? If yes, go to step 14 . If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the IAT sensor. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and the low reference circuit at the IAT sensor. Turn ignition on, with engine off. Observe the IAT sensor temperature with a scan tool. Is the IAT sensor temperature more than 262°F (128°C)? If yes, go to step 10 . If no, go to next step.
Turn ignition off. Connect a 3-amp fused jumper wire between the signal circuit of the IAT sensor and a known-good ground. Turn ignition on, with engine off. Observe the IAT sensor temperature with a scan tool. Is the IAT sensor temperature more than 262°F (128°C)? If yes, go to step 9 . If no, go to next step.
Test the signal circuit of the IAT sensor for an open circuit or high resistance. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Test the IAT sensor low reference circuit for high resistance or an open. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Inspect for poor connections at the harness connector of the IAT sensor. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the harness connector of the PCM. Repair the connections as necessary. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the IAT sensor. After replacing sensor, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.

If a short to a separate 5-volt source occurs this DTC may set. If this condition exists, a continuity test to all other PCM 5-volt reference circuits will be necessary. If an intermittent condition is suspected, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0116: ECT SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Engine Coolant Temperature (ECT) sensor is a variable resistor that measures the temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 volts to the signal circuit. When coolant temperatures are low, resistance is high. When coolant temperatures are high the resistance is low. The PCM uses this input for engine controls and enabling criteria for diagnostics. The PCM will record the amount of time the engine is OFF. At restart the PCM will compare the temperature difference between the ECT and Intake Air Temperature (IAT). If the temperature difference is not within the calculated amount, after the predetermined soak time, this DTC will set.

Before failing this test, the PCM will test for the presence of a block heater.

The ignition is ON.
DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, P1621, or P1683 are not set.
The vehicle has a minimum soak time of 8 hours.

If the PCM detects a temperature difference of more than 27°F (915°C) between the ECT and the IAT, the vehicle must be driven for 5 minutes over 15 MPH. If the IAT decreases more than 12.6°F (7°C) then a block heater is indicated and the test is aborted. If the IAT temperature does not decrease, a block heater was not detected and this DTC will set.
The temperature difference between ECT and IAT at start-up is greater than 252°F (140°C).
The time spent cranking the engine, without starting is greater than 10 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

3 This step tests for excessive resistance in the ECT sensor circuit.
4 This step tests for excessive resistance in the IAT sensor circuit.
5 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is the cooling system low on coolant? If yes, check and repair cause of loss of loss of coolant. If no, go to next step.
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the ECT sensor. Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? If yes, go to next step. If no, go to step 5 .
Turn ignition off. Disconnect the IAT sensor. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the IAT sensor. Turn ignition on, with engine off. With a scan tool, observe the IAT sensor temperature. Does the scan tool indicate that the IAT sensor temperature is more than 280°F (138°C)? If yes, go to step 8 . If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and a known-good ground. Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? If yes, go to next step. If no, go to step 7 .
Test the ECT sensor low reference circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step 11 .
Test the ECT sensor signal circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step 11 .
Remove the ECT sensor. Suspend the ECT sensor and a thermometer in a pan of water. Place the pan on a burner or hot plate. Test the resistance of the ECT sensor through the specified range of 50-194°F (10-90°C). Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article. Does the resistance and temperature closely match the Temperature-to-Resistance table? If yes, go to next step. If no, go to step 10 .
Reinstall the ECT sensor. When complete, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Replace the ECT sensor. After replacing sensor, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0116 is designed to detect an ECT sensor that is skewed high.
An IAT sensor that is skewed low could cause this DTC to set.
When inspecting the ECT sensor, the Temperature-vs-Resistance table should be used in order to determine if a skewed sensor is the problem. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.
If the engine has been allowed to sit overnight, the ECT and IAT temperature should be within the calculated amount.

DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Engine Coolant Temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures the temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 volts to the ECT signal circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively low ECT signal voltage, which is a high temperature indication, DTC P0117 sets.

The engine is running.

The ECT sensor indicates an engine coolant temperature more than 283°F (140°C).
The above condition is met for more than 15 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Observe the Engine Coolant Temperature (ECT) parameter on the scan tool. Is the ECT more than 280°F (138°C)? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records that you observed. Does the DTC reset? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Disconnect ECT sensor harness connector. Turn ignition on, with engine off. Observe ECT parameter on scan tool. Is ECT parameter is less than -36°F (-38°C)? If yes, go to step 6 . If no, go to next step.
Turn ignition off. Disconnect PCM harness connectors. Test the signal circuit of the ECT sensor for a short to ground or a short to ECT low reference circuit. Did you find and correct the condition? If yes, go to step 8 . If no, go to step 7 .
Replace ECT sensor. After replacing sensor, go to step 8 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. If any undiagnosed DTCs are present, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are present, system is okay.

An overheating condition may cause this DTC to set.
After starting the engine, the ECT sensor temperature should rise steadily to about 194°F (90°C) then stabilize when the thermostat opens.
Use the Temperature-vs-Resistance value table in order to test the ECT sensor at various temperature levels, in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.
If the malfunction is not present at this time, refer to «DTC P1114: ECT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p1114-ect-sensor-circuit-intermittent) .
If an intermittent condition is suspected, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Engine Coolant Temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures the temperature of the engine coolant. The ECT sensor has a signal circuit and a low reference circuit. The Powertrain Control Module (PCM) supplies 5 volts to the ECT signal circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively high ECT signal voltage, which is a low temperature indication, DTC P0118 sets.

The engine is running.

The ECT sensor temperature is less than -36°F (-38°C) for more than 15 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 This step tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Using scan tool, observe ECT sensor parameter on scan tool. Does the scan tool indicate that the ECT sensor temperature is less than -36°F (-38°C)? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for running the DTC or as close to the Freeze Frame/Failure Records that you observed. Does the DTC reset? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and the low reference circuit at the ECT sensor. Turn ignition on, with engine off. Observe the ECT sensor temperature with a scan tool. Does the scan tool indicate ECT sensor temperature more than 280°F (138°C)? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and a known-good ground. Turn ignition on, with engine off. Observe the ECT sensor temperature with a scan tool. Does the scan tool indicate ECT sensor temperature more than 280°F (138°C)? If yes, go to step 7 . If no, go to next step.
Test the signal circuit of the ECT sensor a short to voltage, high resistance or open circuit. Repair the circuit as necessary. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Test the ECT sensor low reference circuit for high resistance or an open. Repair the circuit as necessary. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Inspect for poor connections at the harness connector of the ECT sensor. Repair the connections as necessary. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
Inspect for poor connections at the harness connector of the PCM. Repair the connections as necessary. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Replace ECT sensor. After replacing sensor, go to step 12 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

If a short to a separate 5 volt source occurs, this DTC may set. If this condition exists, a continuity test to all other PCM circuits will be necessary to diagnose the specific circuit.
After starting the engine, the ECT should rise steadily to about 194°F (90°C) then stabilize when the thermostat opens.
Use the Temperature-vs-Resistance table to test the ECT sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability concerns. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.
If a malfunction is not present at this time, refer to «DTC P1115: ECT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p1115-ect-sensor-circuit-intermittent) .
If an intermittent condition is suspected, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0121: THROTTLE POSITION SENSOR PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits: A 5-volt reference circuit, low reference circuit and signal circuit.

The PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. When the conditions for running this DTC are met the PCM will use the Manifold Absolute Pressure (MAP) sensor to determine if the predicted operating range of the TP sensor is correct. A skewed MAP sensor may cause this DTC to set and should be tested for proper operation if the TP sensor is determined to be operating properly and this DTC continues to set.

DTCs P0107, P0108, P0122, P0123, P1106, P1107, P1121, or P1122 are not set.
The engine has been running for more than 2 minutes.
The Engine Coolant Temperature (ECT) is more than 167°F (75°C).
The MAP reading is less than 50 kPa for a TP sensor skewed high test.
The MAP reading is more than 70 kPa for a TP sensor skewed low test.
The MAP is steady for 5 seconds or more.

The TP sensor reading is more than a predicted value when the MAP is less than 50 kPa.
The TP sensor reading is less than a predicted value when the MAP is greater than 70 kPa.
The above conditions are present for 5 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. Observe the Throttle Position (TP) sensor parameter on the scan tool while slowly opening the throttle to Wide Open Throttle (WOT). Does the TP sensor value increase steadily and evenly from the closed throttle value of 0 percent to greater than WOT value of 98 percent? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the TP sensor harness connector. Turn ignition on, with engine off. Observe the TP sensor voltage parameter with a scan tool. Does the scan tool indicate TP sensor voltage at 0 volts? If yes, go to next step. If no, go to step 6 .
Turn ignition off. Connect a fused jumper wire between the 5-volt reference circuit and the signal circuit at the TP sensor harness connector. Turn ignition on, with engine off. Observe the TP sensor voltage parameter with a scan tool. Does the scan tool indicate TP sensor voltage at 5 volts? If yes, go to step 9 . If no, go to step 7 .
Test the TP sensor signal circuit for a short to voltage with the DMM. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 12 .
Test the TP sensor 5-volt reference circuit for an open or high resistance with the DMM. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
Test the TP sensor signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 11 .
Test the TP sensor low reference circuit for an open or high resistance. Did you find and correct the condition? If yes, 15 . If no, go to next step.
Test the TP sensor 5-volt reference circuit for high resistance. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
Inspect for a poor connection at the TP sensor harness connector. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 13 .
Inspect for a poor connection at the Powertrain Control Module (PCM) harness connector. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 14 .
Replace the TP sensor. After replacing sensor, go to step 15 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe the stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

A skewed MAP signal may cause the PCM to incorrectly determine the TP sensor is out of range. Inspect for an unusually low or high MAP reading.

If the DTC is determined to be intermittent or TP sensor system is still suspect, refer to DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE .

DTC P0122: THROTTLE POSITION SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with a 5-volt reference circuit, low reference circuit and a signal circuit.

The ignition is ON.

The TP sensor signal voltage is less than 0.1 volt.
The above condition is present for at least 1 second.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

8 Malfunctioning components that share the TP sensor 5-volt reference circuit could cause a low voltage condition on this circuit.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. Observe the Throttle Position (TP) voltage parameter with a scan tool. Does the scan tool indicate that the TP sensor voltage is less than 0.1 volt? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p1121-tp-sensor-circuit-intermittent) .
Turn ignition off. Disconnect the TP sensor harness connector. Connect a fused jumper wire between the TP sensor 5-volt reference circuit and the TP sensor signal circuit at the TP sensor harness connector. Turn ignition on, with engine off. Observe the TP sensor voltage parameter with a scan tool. Does the scan tool indicate TP sensor voltage at 5 volts? If yes, go to step 11 . If no, go to next step.
Disconnect the fused jumper wire. Test for voltage between the 5-volt reference circuit of the TP sensor and the low reference circuit of the TP sensor with the Digital Multimeter (DMM). Does the DMM indicate voltage near 5 volts? If yes, go to step 9 . If no, go to next step.
Test the TP sensor 5-volt reference circuit for an open or high resistance with the DMM. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Test all 5-volt reference circuits for a short to ground. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
With a DMM connected between the TP sensor 5-volt reference circuit and the TP sensor low reference circuit, observe voltage while disconnecting all sensors, one at a time, that use a 5-volt reference signal. A change in voltage indicates the faulty component. Replace that component as necessary. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
Test the TP sensor signal circuit with the DMM for an open, short to ground, or high resistance. Repair as necessary. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Inspect for poor connections at the Powertrain Control Module (PCM) harness connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Inspect for poor connections at the TP sensor harness connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Replace the TP sensor. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0123: THROTTLE POSITION SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with a 5-volt reference circuit, low reference circuit and a signal circuit.

The ignition is ON.

TP sensor signal voltage is more than 4.9 volts.
The above condition is present for at least 1 second.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. Observe the Throttle Position (TP) sensor voltage parameter with the throttle closed with a scan tool. Does the scan tool indicate that the TP sensor voltage is greater than 4.9 volts? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p1121-tp-sensor-circuit-intermittent) .
Turn ignition off. Disconnect the TP sensor. Turn ignition on, with engine off. Observe the TP sensor voltage parameter with a scan tool. Does the scan tool indicate that the TP voltage is at 0 volts? If yes, go to next step. If no, go to step 7 .
Measure the voltage from the 5-volt reference circuit of the TP sensor to a known-good ground. Does the voltage measure near 5 volts? If yes, go to next step. If no, go to step 8 .
Test the low reference circuit of the TP sensor for a high resistance or for an open. Did you find and correct the condition? If no, go to step 13 . If yes, go to step 10 .
Test the signal circuit of the TP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 10 .
Test all 5-volt reference circuits for a short to voltage. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 10 .
Inspect for poor connections at the harness connector of the TP sensor. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 11 .
Inspect for poor connections at the harness connector of the Powertrain Control Module (PCM). Did you find and correct the condition? If yes, go to step 13 . If no, go to step 12 .
Replace TP sensor. After replacing sensor, go to step 13 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0125: ECT EXCESSIVE TIME TO ENTER CLOSED LOOP

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

An Engine Coolant Temperature (ECT) sensor monitors the temperature of the coolant. This input is used by the Powertrain Control Module (PCM) for engine control and as an enabling criteria for some diagnostics.

The air flow coming into the engine is accumulated and used to determine if the engine has been driven within conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach regulating temperature of the thermostat, diagnostics that use engine coolant temperature as enabling criteria may not run when expected.

This DTC will set when there has been excessive time to reach a minimum coolant temperature required for Closed Loop fuel control.

This DTC will only run once per ignition cycle within enabling conditions.
DTCs P0112, P0113, P0116, P0117, P0118, P1111, P1112, P1114, or P1115 are not set.
The minimum intake air temperature is more than 19°F (-7°C).
The start-up Engine Coolant Temperature (ECT) is -40 to 104°F (-40 to 40°C).

The engine run time is over 5 minutes to achieve Closed Loop temperature of 14°F (-10°C).
The calibrated amount air flow has been exceeded.
The maximum idle time has been less than 4 minutes.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

3 This step tests for excessive resistance in the ECT circuit.
7 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is the cooling system low on coolant? If yes, check and repair cause of coolant loss. If no, go to next step.
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the ECT sensor harness connector. Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? If yes, go to step 7 . If no, go to next step.
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor harness connector and a known-good ground. Turn ignition on, with engine off. Observe the ECT sensor temperature with a scan tool. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? If yes, go to next step. If no, go to step 6 .
Test the ECT sensor low reference circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step 10 .
Test the ECT sensor signal circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step 10 .
Remove the ECT sensor. Suspend the ECT sensor and a thermometer in a pan of water. Place the pan on a burner or hot plate. Test the resistance of the ECT sensor through the specified range of 50-194°F (10-90°C). Does the resistance and temperature closely match the Temperature-vs-Resistance table? Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article. If yes, go to next step. If no, go to step 9 .
Reinstall the ECT sensor. When complete, diagnose thermostat operation.
Replace the ECT sensor. After replacing sensor, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are displayed, system is okay.

DTC P0125 is designed to detect a skewed ECT sensor.

DTC P0128: ENGINE COOLANT THERMOSTAT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The air flow coming into the engine is accumulated and used to determine if the engine has been driven within conditions that would allow the engine coolant to heat up normally to the thermostat regulating temperature. If the coolant temperature does not increase normally or does not reach regulating temperature of the thermostat, diagnostics that use the ECT as enabling criteria, may not run when expected.

If engine coolant fails to reach a preset target temperature before a calculated air flow is accumulated DTC P0128 will set.

This DTC will only run once per ignition cycle within enabling conditions.
DTCs P0112, P0113, P0116, P0117, P0118, P1111, P1112, P1114, or P1115 are not set.
The coolant temperature is more than -40°F (-40°C).
The coolant temperature is less than 172°F (78°C).
The intake air temperature is more than 19°F (-7°C).
The engine is running more than 2 minutes, and less than 30 minutes.
The vehicle speed is more than 15 MPH for more than 1 mile (1.6 km).
The Mass Airflow (MAF) average reading is more than 15 g/s.

The length of time for the engine coolant to reach a preset temperature of 170°F (80°C) has been exceeded.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

3 This step tests for excessive resistance in the ECT circuit.
7 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is the cooling system low on coolant? If yes, check and repair cause of coolant loss. If no, go to next step.
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the ECT sensor. Turn ignition on, with engine off. Observe the ECT sensor temperature with a scan tool. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? If yes, go to step 7 . If no, go to next step.
Turn ignition off. Disconnect the ECT sensor. Connect a 3-amp fused jumper wire between the signal circuit of the ECT sensor and a known-good ground. Turn ignition on, with engine off. Observe the ECT sensor temperature with a scan tool. Does the scan tool indicate that the ECT sensor temperature is more than 280°F (138°C)? go to next step. If no, go to step 6 .
Test the ECT sensor reference low circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step 10 .
Test the ECT sensor signal circuit for a high resistance or an open. Repair the circuit as necessary. After repairs, go to step 10 .
Remove the ECT sensor. Suspend the ECT sensor and a thermometer in a pan of water. Place the pan on a burner or hot plate. Test the resistance of the ECT sensor through the specified range of 50-194°F (10-90°C). Does the resistance and temperature closely match the Temperature-vs-Resistance table? Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article. If yes, go to next step. If no, go to step 9 .
Reinstall the ECT sensor. After replacing sensor, diagnose thermostat operation.
Replace the ECT sensor. After replacing sensor, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0128 is designed to detect a faulty thermostat.
A skewed ECT sensor may cause a DTC P0128 to set.
If a DTC P0125 and P0128 are both set, a skewed ECT sensor is the most likely cause.
A skewed Intake Air Temperature (IAT) sensor may cause this DTC to set.

DTC P0130: HO2S CIRCUIT (SENSOR 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. This DTC will set if the PCM receives an active HO2S 1 signal of a lower than calibrated minimum amplitude.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage and heater low control.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The engine has been running for at least 4 minutes.
The Mass Airflow (MAF) is 8-35 g/s.
The engine speed is 550-3000 RPM.
The throttle angle is 3-35 percent.
The system voltage is 9-18 volts.
The ECT is more than 158°F (70°C).

The PCM detects an active sensor with an improper voltage signal amplitude.

PCM illuminates the Malfunction Indicator Light (MIL) after 2 consecutive ignition cycles in which the diagnostic runs with the fault active.
The PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

The PCM turns off the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the Bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.
6 This step inspects the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.
8 This step inspects for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.
9 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage fluctuate rapidly at greater than 350 mV and less than 550 mV? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a Digital Multimeter (DMM). Is the HO2S voltage within 0.425-0.500 volt? If yes, go to next step. If no, go to step 6 .
Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit, and the HO2S 1 low signal circuit. Turn ignition on, with engine off. Observe the HO2S 1 voltage on the scan tool. Does the scan tool display less than 25 mV? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Disconnect both PCM connectors. Measure the resistance of each of the following circuits with a DMM: HO2S 1 high signal circuit between HO2S connector and PCM connector, HO2S 1 low signal circuit between HO2S connector and PCM connector, and HO2S 1 low reference circuit between PCM harness connector terminals No. C1-29 and C2- 80. Is the resistance of each circuit less than 5 ohms? If yes, go to step 11 . If no, go to next step.
Repair the circuit that measured a high resistance or an open. After repairs, go to step 14 .
Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S 1 ignition voltage circuit and the HO2S 1 heater low control circuit terminals, on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to «DTC P0135: HO2S HEATER PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0135-ho2s-heater-performance) .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the HO2S 1 sensor. After replacing sensor, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0131: HO2S CIRCUIT - LOW VOLTAGE (BANK 1; SENSOR 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage remains less than a calibrated amount for an excessive amount of time.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage and heater low control circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, and P1441 are not set.
The system voltage is 9-18 volts.
The Closed Loop commanded air/fuel ratio is 12.0-16.5.
The throttle angle is 3-35 percent.

The DTC will set if either of the following conditions are present for up to 50 seconds

The HO2S 1 signal voltage remains less than 175 mV during Closed Loop operation.
The HO2S 1 signal voltage remains less than 600 mV during Power Enrichment (PE) mode.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM turns OFF the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than bias voltage in this step indicates a short circuit condition in the high signal circuit.
6 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage remain less than 175 mV? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Observe the HO2S 1 voltage parameter with a scan tool. Does the HO2S voltage read less than 175 mV? If yes, go to next step. If no, go to step 6 .
Test the HO2S 1 high signal circuit for a short to ground. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 8 .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 11 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 9 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Replace the HO2S 1 sensor. After repairs, go to step 11
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0132: HO2S CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage remains greater than a calibrated amount for an excessive amount of time.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage and heater low control circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The system voltage is 9-18 volts.
The Closed Loop commanded air/fuel ratio is 12.0-16.5.
The throttle angle is 3-35 percent.

The DTC will set if either of the following conditions are present for up to 55 seconds

The HO2S 1 signal voltage remains greater than 975 mV during Closed Loop operation for longer than 45 seconds.
The HO2S 1 signal voltage remains greater than 200 mV during Decel Fuel Cut-Off (DFCO) operation.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

The PCM turns OFF the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the Bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than bias voltage in this step indicates a short circuit condition in the high signal circuit.
6 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage remain greater than 975 mV? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Observe the HO2S 1 voltage parameter with a scan tool. Does the HO2S 1 voltage remain greater than 975 mV? If yes, go to next step. If no, go to step 6 .
Test the HO2S 1 high signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 8 .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 11 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 9 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Replace HO2S 1. After replacing sensor, go to step 11 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are set, system is okay.

DTC P0133: HO2S SLOW RESPONSE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage average response time is too slow.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage and heater low control circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The vehicle is not in Park or Neutral.
The engine has been running for at least 4 minutes.
The Mass Airflow (MAF) is 8-35 g/s.
The engine speed is 550-3000 RPM.
The throttle angle is 3-35 percent.
The system voltage is 9-18 volts.
The engine coolant temperature is greater than 158°F (70°C).

DTC will set if either of the following conditions are present

The HO2S 1 rich-to-lean transition time takes longer than 105 milliseconds.
The HO2S 1 lean-to-rich transition time takes longer than 95 milliseconds.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

PCM turns OFF the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the Bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.
6 This step inspects the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.
8 This step inspects for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.
9 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage fluctuate rapidly greater than and less than 350-550 mV? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a Digital Multimeter (DMM). Is the HO2S voltage within 0.425-0.500 volt? If yes, go to next step. If no, go to step 6 .
Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 1 harness connector high signal circuit and low reference circuit. Turn ignition on, with engine off. Observe the HO2S 1 voltage on the scan tool. Does the scan tool display less than 25 mV? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Disconnect both PCM connectors. Measure the resistance of each of the following circuits with a DMM: HO2S 1 high signal circuit between HO2S connector and PCM connector, HO2S 1 low reference circuit between HO2S connector and PCM connector, HO2S 1 low reference loop between PCM harness connector terminals VC1-29 and VC2-80. Is resistance of each circuit less than 5 ohms? If yes, go to step 11 . If no, go to next step.
Repair the circuit that measured a high resistance or an open. After repairs, go to step 14
Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S heater ignition voltage circuit, and heater low control circuit terminals on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to «DTC P0135: HO2S HEATER PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0135-ho2s-heater-performance) .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the HO2S 1 sensor. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are set, system is okay.

DTC P0134: HO2S CIRCUIT INSUFFICIENT ACTIVITY

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage remains at or near the bias voltage amount.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage and heater low control circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The engine has been running for at least 4 minutes.
The system voltage is 9-18 volts.

HO2S 1 signal voltage remains between 350-550 mV for more than 30 seconds.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM turns OFF the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.
6 This step inspects the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.
8 This step inspects for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.
9 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage fluctuate rapidly greater than and less than 350-550 mV? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a Digital Multimeter (DMM). Is the HO2S voltage within 0.425-0.500 volt? If yes, go to next step. If no, go to step 6 .
Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 1 harness connector high signal circuit and low reference circuit. Turn ignition on, with engine off. Observe the HO2S 1 voltage on scan tool. Does scan tool display less than 25 mV? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Disconnect both PCM connectors. Measure the resistance of each of the following circuits with a DMM: HO2S 1 high signal circuit between HO2S connector and PCM connector, HO2S 1 low reference circuit between HO2S connector and PCM connector. Is resistance of each circuit less than 5 ohms? If yes, go to step 11 . If no, go to next step.
Repair the circuit that measured a high resistance or an open. After repairs, go to step 14 .
Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S heater ignition voltage circuit and heater low control circuit terminals on engine harness side. Start engine. Does test light illuminate? If yes, go to next step. If no, go to «DTC P0135: HO2S HEATER PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0135-ho2s-heater-performance) .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the HO2S 1. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0135: HO2S HEATER PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The PCM controls the HO2S 1 heater low control circuit with a low side driver. The HO2S 1 heater diagnostic monitors the current draw through the HO2S 1 low side driver when the engine is running. This DTC will set if the current level is not within the calibrated range.

Each HO2S 1 has the following circuits: High signal, low reference, heater ignition voltage and heater low control circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The system voltage is 9-18 volts.
The engine has been running for at least 4 minutes.
The ECT is more than 158°F (70°C).
The engine speed is 650-2500 RPM.
The Mass Airflow (MAF) is 4-26 g/s.

The HO2S 1 heater current is not within the calibrated range.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

PCM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 Inspect the heater current with the engine at operating temperature, and allow time for the heater current to stabilize. The HO2S 1 heater current is initially higher until the sensor reaches full operating temperature.
4 This step ensures that the ignition voltage circuit to the HO2S 1 is not open or shorted. The test light should be connected to a good chassis ground, in case the HO2S 1 low reference or HO2S 1 heater low control circuit is malfunctioning.
6 This step inspects the HO2S 1 heater ground circuit. The engine must be running for the PCM to enable the heater low control driver to provide a path to ground.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Monitor the HO2S 1 Heater Current parameter on a scan tool. Allow the current to stabilize. Is the HO2S 1 Heater Current within 0.25-0.85 A? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Disconnect the HO2S 1 electrical connector. Turn ignition on, with engine off. Probe the HO2S heater ignition voltage circuit at the HO2S 1 electrical connector, PCM harness side, with a test light connected to ground. Does the test light illuminate? If yes, go to step 6 . If no, go to next step.
Test the HO2S 1 heater ignition voltage fuse. Is the fuse open? If yes, go to step 11 . If no, go to step 12 .
Turn ignition off. Connect a test light between the HO2S 1 ignition 1 voltage circuit and the HO2S 1 heater low control circuit. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to step 8 .
Leave the test light connected between the HO2S 1 heater ignition voltage circuit and the HO2S 1 heater low control circuit. Turn ignition off. Turn ignition on, with engine off. Does the test light illuminate? If yes, go to step 9 . If no, go to step 13 .
Turn ignition off. Disconnect the PCM connector containing the HO2S 1 heater low control circuit. Measure the resistance of the HO2S heater low control circuit between the PCM harness connector, and the HO2S harness connector using a DMM. Is the resistance within 0-5 ohms? If yes, go to step 15 . If no, go to step 10 .
Test the HO2S 1 heater low control circuit for a short to ground. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 15 .
Test the HO2S 1 heater low control circuit for an open or high resistance condition. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 15 .
Test the HO2S 1 heater ignition voltage circuit for a short to ground and replace the fuse. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 15 .
Test the HO2S 1 heater ignition voltage circuit for an open or high resistance condition. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 15 .
At the disconnected HO2S 1 pigtail connector test the HO2S heater ignition voltage circuit for continuity between the HO2S 1 high signal, low signal, sensor outer shell or a good ground. Do any of the circuits measure other than infinite resistance? If yes, go to step 16 . If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Inspect for poor connections at the harness connector of the HO2S 1. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 18 , If no, go to step 17 .
Replace the HO2S 1. After repairs, go to step 18
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0137: HO2S CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The HO2S 2 is used for post catalyst monitoring. This DTC will set if the HO2S 2 voltage remains less than a calibrated amount for an excessive amount of time.

The HO2S 2 has the following circuits: High signal, low signal, heater ignition voltage and heater ground circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The system voltage is 9-18 volts.
The system is in Closed Loop.
The air/fuel ratio is 12-16.5.
The throttle angle is 3-40 percent.

The minimum voltage is more than 500 mV for 4 seconds, while operating in the fuel cutoff mode.

The HO2S 2 signal voltage remains less than 30 mV during Closed Loop operation.
The HO2S 2 signal voltage remains less than 550 mV during Power Enrichment (PE) mode.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM turns OFF the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 2 voltage may default to the Bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 2 voltage signal will fluctuate greater than and less than the bias voltage amount. The action in the test step should result in a visible reaction from the HO2S 2 output.
4 A voltage reading other than bias voltage in this step indicates a short circuit condition in the high signal circuit.
7 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 2 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Vary the engine speed from idle to 3000 RPM several times within 5 seconds. Did the HO2S 2 voltage remain less than 30 mV? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Disconnect the HO2S 2 connector. Turn ignition on, with engine off. Observe the HO2S 2 voltage parameter with a scan tool. Does the HO2S voltage read less than 30 mV? If yes, go to next step. If no, go to step 6 .
Test the HO2S 2 high signal circuit for a short to ground. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Test the HO2S 2 low signal circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Inspect for poor connections at the HO2S 2 connector. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Replace the HO2S 2. After repairs, go to step 12
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0138: HO2S CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The HO2S 2 is used for post catalyst monitoring. This DTC will set if the HO2S 2 voltage remains greater than a calibrated amount for an excessive amount of time.

Each HO2S 2 has the following circuits: High signal, low signal, heater ignition voltage and heater ground circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The system voltage is 9-18 volts.
The Closed Loop commanded air/fuel ratio is 14.5-14.8.
The throttle angle is 3-40 percent.

The HO2S 2 signal voltage remains greater than 975 mV during Closed Loop operation for longer than 45 seconds or HO2S 2 signal voltage remains greater than 200 mV during Decel Fuel Cut-Off (DFCO) operation, with either conditions present for up to 5 minutes.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
PCM records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the PCM stores this information in the failure records. If the diagnostic reports a failure on the second consecutive ignition cycle, the PCM records the operating conditions at the time of the failure. The PCM writes the operating conditions to the Freeze Frame and updates the Failure Records.

PCM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

3 The HO2S 2 voltage may default to the Bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 2 voltage signal will fluctuate greater than and less than the bias voltage amount. The action in the test step should result in a visible reaction from the HO2S 2 output.
5 A voltage reading other than bias voltage in this step indicates a short circuit condition in the high signal circuit.
7 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Did DTC P0140 also set? If yes, go to «DTC P0140: HO2S CIRCUIT INSUFFICIENT ACTIVITY (BANK 1; SENSOR 2)»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0140-ho2s-circuit-insufficient-activity) . If no, go to next step.
Allow the engine to idle at operating temperature. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Vary the engine speed from idle to 3000 RPM several times within 5 seconds. Observe the HO2S 2 voltage parameter with a scan tool. Did the HO2S 2 voltage remain greater than 975 mV? If yes, go to step 5 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 2 connector. Connect a 3-amp fused jumper wire between the HO2S 2 low signal circuit and a good ground. Turn ignition on, with engine off. Observe the HO2S 2 voltage parameter with a scan tool. Does the HO2S voltage read more than 975 mV? If yes, go to next step. If no, go to step 7 .
Test the HO2S 2 high signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Inspect for poor connections at the HO2S 2 connector. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Replace the HO2S 2. After repairs, go to step 12
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 3 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0140: HO2S CIRCUIT INSUFFICIENT ACTIVITY (BANK 1; SENSOR 2)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The HO2S 2 is used for post catalyst monitoring. This DTC will set if the HO2S 2 voltage remains at or near the bias voltage amount.

Each HO2S 2 has the following circuits: High signal, low signal, heater ignition voltage and heater ground circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The engine run time is longer than 4 minutes.
The system voltage is 9-18 volts.
The diagnostic runs once per trip.

HO2S 2 signal voltage remains between 408-512 mV for more than 90 seconds.
There is a Throttle Position (TP) sensor angle change of more than 8 percent, at least twice during the test period.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

PCM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 2 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 2 voltage signal will fluctuate greater than and less than the bias voltage amount. The action in the test step should result in a visible reaction from the HO2S 2 output.
4 A voltage reading other than the specified amount in this step indicates an open circuit condition in one of the signal circuits or the PCM.
5 This step inspects for an open circuit condition in the signal circuits, independent of the PCM.
7 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 2 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 2 voltage is fixed at bias voltage. Vary the engine speed from idle to 3000 RPM several times within 5 seconds. Does the HO2S 2 voltage fluctuate greater than and less than 375-475 mV? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Disconnect the HO2S 2 connector. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the HO2S 2 low signal circuit and a good ground. Connect a 3-amp fused jumper wire between the HO2S 2 high signal circuit and a good ground. Observe the HO2S 2 voltage parameter with a scan tool. Does the HO2S 2 voltage measure less than 25 mV? If yes, go to step 7 . If no, go to next step.
With the ignition OFF disconnect the PCM. Leave the HO2S 2 disconnected. Measure the resistance of the HO2S 2 high signal circuit. Measure the resistance of the HO2S 2 low signal circuit. Is the resistance within 0-5 ohms? If yes, go to step 9 . If no, go to next step.
Repair the signal circuit that has an open or high resistance condition. After repairs, go to step 12 .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Inspect for poor connections at the HO2S 2 connector. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Replace the HO2S 2. After repairs, go to step 12 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0141: HO2S HEATER PERFORMANCE (BANK 1; SENSOR 2)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The HO2S 2 heater performance diagnostic will only run from a cold start and only once per key cycle. This DTC will set if the HO2S 2 heater takes too long to heat based on the HO2S 2 signal voltage input to the PCM. The HO2S 2 heater circuit is energized anytime the ignition key is in the ON position.

The HO2S 2 has the following circuits: High signal, low signal, heater ignition voltage and heater ground circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The system voltage is 9-18 volts.
The IAT is less than 35°F (2°C) at start-up.
The ECT is less than 35°F (2°C) at start-up.
The IAT and ECT are within 11°F (6°C) of each other at start-up.

HO2S 2 voltage remains within 150 mV of the bias voltage, about 450 mV, for a longer amount of time than necessary. The amount of time ranges between 100-130 seconds depending on ECT at start-up and average Mass Airflow (MAF) since start-up.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current DTC last test fails clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 2 should be allowed to cool before performing this test. The HO2S 2 is cool enough if the voltage output is stable at bias or about 450 mV. If the HO2S 2 heater is functioning, the signal voltage will gradually change as the sensor element warms. If the heater is not functioning, the HO2S 2 signal will remain near the 450 mV bias voltage or show very little activity.
4 This step ensures that the ignition voltage circuit to the HO2S 2 is not open or shorted. The test light must be connected to a good ground, independent of the HO2S system
6 This test must not be performed until the HO2S 2 heater has cooled and stabilized for at least 15 minutes. Heater resistance is typically about 5 ohms at room temperature.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. Monitor HO2S 2 voltage on the scan tool. Does the HO2S 2 voltage go to greater than or less than the previously stabilized voltage, by at least as much as 100 mV within 2 minutes? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Disconnect the HO2S 2 electrical connector. Turn ignition on, with engine off. Connect a test light between the HO2S 2 heater ignition voltage circuit, in the harness side of the HO2S connector, and ground. Does the test light illuminate? If yes, go to next step. If no, go to step 7 .
Turn ignition off. Connect a test light between the HO2S 2 heater ignition voltage circuit, in the harness side of the HO2S connector, and the HO2S 2 heater ground circuit. Turn ignition on, with engine off. Does the test light illuminate? If yes, go to next step. If no, go to step 10 .
Turn OFF ignition. Leave HO2S connector disconnected. Allow engine to cool for at least 15 minutes. Measure HO2S 2 heater resistance at HO2S 2 pigtail connector using a Digital Multimeter (DMM). Resistance should be within 2-20 ohms? If yes, go to next step. If no, go to step 11 .
Test the HO2S 2 heater ignition voltage circuit for an open fuse. Did you find an open fuse? If yes, go to next step. If no, go to step 9 .
Locate and repair the short to ground in the HO2S 2 heater ignition voltage circuit and replace the fuse. After repairs, go to step 13 .
Repair the open or high resistance condition in the HO2S 2 heater ignition voltage circuit. After repairs, go to step 13 .
Repair the open or high resistance condition in the HO2S 2 heater ground circuit. After repairs, go to step 13 .
Before continuing, inspect for poor connections at the HO2S 2 connector. Did you find and correct the condition? If yes, go to step 13 . If no, go to next step.
Replace the HO2S 2. After repairs, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0171: LEAN FUEL TRIM SYSTEM (BANK 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals, without oxygen sensor input. During Closed Loop, the PCM adds oxygen sensor inputs to calculate short and long term fuel trim, fuel delivery adjustments. If the oxygen sensors indicate a lean condition, the fuel trim values will be greater than 0 percent. If the oxygen sensors indicate a rich condition, the fuel trim values will be less than 0 percent. The short term fuel trim values change rapidly in response to the HO2S voltage signals. The long term fuel trim makes coarse adjustments in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, this DTC will set.

DTCs P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0410, P0440, P0442, P0446, P0506, P0507, P1404, or P1441 are not set.
The ECT is 68-230°F (20-110°C).
The intake air temperature is 64-158°F (18-70°C).
The MAP is 2.6-15.2 psi (18-105 kPa).
The vehicle speed is less than 82 MPH.
The engine speed is 550-4000 RPM.
The BARO is more than 10.1 psi (70 kPa).
The MAF is 2.8-150 g/s.
The fuel level is more than 10 percent.

The average long term fuel trim value is greater than 20 percent for 6 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 If no condition was found, diagnose refer fuel system for possible fuel condition.
6 If no conditions are found, a worn cam, worn intake, or exhaust valves, or other engine mechanical failures may be at fault.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start and idle the engine at normal operating temperature in Closed Loop. Record the Long Term fuel trim data. Turn OFF the engine. Turn ignition on, with engine off. Review the Freeze Frame Records/Failure Records and record displayed data for this DTC. Does the scan tool indicate that the Long Term Fuel Trim is greater than 23 percent? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Operate engine at idle. Observe the HO2S parameters with a scan tool. Does the scan tool indicate that the values are within 200-800 mV and fluctuating? If yes, go to next step. If no, go to step 5 .
Turn OFF engine. Inspect vacuum hoses for splits, kinks, and proper connections. Check for fuel contamination. Ensure vehicle has sufficient fuel. If fuel pressure is too low, this DTC may set. Did you find and correct the condition? If yes, go to step 7 . If no, go to step 6 .
Turn OFF the engine. Inspect the HO2S for proper installation. Ensure that the electrical connectors and the wires are secured and not contacting the exhaust system. Inspect for a short between the signal circuit and the low reference circuit. Did you find and correct the condition? If yes, go to step 7 . If no, diagnose fuel system.
Operate the engine at idle. Inspect for missing, loose, or leaking exhaust components. Inspect for vacuum leaks at the intake manifold and injector O-rings. Inspect the air induction system and air intake ducts for vacuum leaks. Inspect the crankcase ventilation system for leaks. Did you find and correct the condition? If yes, go to next step. If no, diagnose engine mechanical problem.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are displayed, system is okay.

The system will go lean if an injector is not supplying enough fuel.
The system will go lean during high fuel demand due to a fuel pump that does not pump enough fuel.
Fuel contamination such as water and alcohol will effect the fuel trim.
Use a scan tool in order to review the Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0172: RICH FUEL TRIM SYSTEM (BANK 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) controls the air/fuel metering system in order to provide the best possible combination of driveability, fuel economy, and emission control. Fuel delivery is controlled differently during Open and Closed Loop. During Open Loop, the PCM determines fuel delivery based on sensor signals, without Oxygen Sensor (O2S) input. During Closed Loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim, delivery adjustments. If the O2S indicate a lean condition, the fuel trim values will be greater than 0 percent. If the O2S indicate a rich condition, the fuel trim values will be less than 0 percent. The short term fuel trim values change rapidly in response to the Heated Oxygen Sensors (HO2S) voltage signals. The long term fuel trim makes coarse adjustments in order to maintain air/fuel ratio of 14.7:1. The fuel trim diagnostic will conduct a test to determine if a rich failure actually exists or if excessive vapor from the Evaporative Emission (EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, this DTC will set. If the PCM detects excessive vapor then a pass is logged.

DTCs P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0130, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0201, P0122, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0410, P0412, P0418, P0440, P0442, P0446, P0506, P0507, P1404, or P1441 are not set.
The ECT is 68-230° F (20-110°C).
The IAT is 64-158°F (18-70°C).
The MAP is 2.1-15.2 psi (15-105 kPa).
The vehicle speed is less than 82 MPH.
The engine speed is 550-4000 RPM.
The BARO is more than 10.1 psi (70 kPa).
The MAF is 2.8-150 g/s.
The fuel level is more than 10 percent.

The average long term fuel trim value is less than less than -13 percent for 40 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 If no condition was found, diagnose fuel system for possible fuel condition.
6 An EVAP canister that is saturated will cause a rich condition. Fuel in the vacuum line to the fuel pressure regulator indicates a bad regulator. If no conditions are found, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be at fault.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start and idle the engine at the normal operating temperature in Closed Loop. Record the long term fuel trim data. Turn OFF the engine. Turn ignition on, with engine off. Review the Freeze Frame/Failure Records and record the displayed data for this DTC. Does the scan tool indicate that the long term fuel trim is less than -13 percent? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Operate the engine at idle. Observe HO2S parameters with a scan tool. Does the scan tool indicate that the values are within 200-800 mV and fluctuating? If yes, go to next step. If no, go to step 5 .
Turn OFF engine. Inspect MAF sensor inlet screen for blockage. Check vacuum hoses for splits, kinks and proper connections. Check for collapsed or restricted air intake duct. Check dirty or restricted air filter. Inspect for objects blocking the throttle body. Did you find and correct the condition? If yes, go to step 7 . If no, go to step 6 .
Turn OFF engine. Inspect HO2S for proper installation. Ensure that the electrical connectors and the wires are secured and not contacting the exhaust system. Did you find and correct the condition? If yes, go to step 7 . If no, diagnose fuel system.
Inspect for excessive fuel in crankcase. Inspect evaporative emissions control system. Inspect fuel pressure regulator for proper operation. Ensure that all injectors are functioning properly. Using scan tool, perform fuel injector balance test. Did you find and correct the condition? If yes, go to next step. If no, diagnose engine mechanical problem.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are displayed, system is okay.

Fuel contamination such as water and alcohol will effect the fuel trim.
A bad MAF sensor can cause a rich condition and set this DTC. Refer to «DTC P0101: MAF SENSOR PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0101-maf-sensor-performance) .
Use a scan tool in order to review Failure Records. If an intermittent condition is suspected, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0201-P0206: INJECTOR CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

P0201 Injector No. 1 Circuit
P0202 Injector No. 2 Circuit
P0203 Injector No. 3 Circuit
P0204 Injector No. 4 Circuit
P0205 Injector No. 5 Circuit
P0206 Injector No. 6 Circuit

The Powertrain Control Module (PCM) enables the appropriate fuel injector for each cylinder. A voltage is supplied directly to the fuel injectors. The PCM controls each fuel injector by grounding the control circuit via a solid state device called a driver. The PCM monitors the status of each driver. If the PCM detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC P0201-P0206 sets.

The engine is running.
The ignition voltage is 9-18 volts.

PCM detects an incorrect voltage on the fuel injector control circuit.
The condition exists for 30 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 This step isolates the condition. If the test light blinks, the PCM is providing ground to the fuel injector. On some vehicles the Camshaft Position (CMP) sensor must provide a signal to the PCM before the PCM will provide a ground to the fuel injector. For this reason, the CMP circuits between the fuel injector harness multi-way connectors must be jumpered.
5 This step tests if a ground is constantly being applied to the fuel injector.
6 This step isolates the circuit between the multi-way connector and the PCM. An open or short to voltage on the fuel injector control circuit will not allow the test light to blink.
8 This step inspects for fuel injector harness damage between the multi-way connector and the upper intake manifold. Careful inspection may isolate the condition before removal of the upper intake manifold.
13 This step isolates the circuit between the multi-way connector and the fuel injector. A short to voltage on the fuel injector control circuit will set this DTC.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Clear the DTCs with a scan tool. Idle the engine at the normal operating temperature. Monitor the misfire current counters with a scan tool. Are any of the misfire current counters incrementing? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close as possible to the Freeze Frame/Failure Records that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the fuel injector harness multi-way connector. Jumper the three Camshaft Position (CMP) sensor circuits between the fuel injector harness multi-way connectors. Probe the appropriate fuel injector control circuit, at the PCM side, of the fuel injector harness multi-way connector with a test light connected to B+. Crank the engine. Does the test light blink when cranking the engine? If yes, go to step 8 . If no, go to next step.
Does the test light remain illuminated at all times? If yes, go to step 7 . If no, go to next step.
Test the control circuit of the fuel injector for a short to voltage or an open between the multi-way connector and the PCM. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 14 .
Test the control circuit of the fuel injector for a short to ground between the multi-way connector and the PCM. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 17 .
Inspect the accessible fuel injector jumper harness between the multi-way connector and the plenum for the following conditions: Poor connections at multi-way connector, damaged or pinched wiring, or broken wires inside insulation. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Remove the upper intake manifold. Probe the appropriate fuel injector control circuit, fuel injector side, at the multi-way connector, with a test light connected to B+. Does the test light illuminate? If yes, go to step 15 . If no, go to next step.
With a DMM, test for continuity between the ignition voltage terminal and the appropriate fuel injector control circuit terminal, at the multi-way connector. Does the DMM indicate OL? If yes, go to next step. If no, go to step 13 .
Test the control circuit of the fuel injector for an open, or poor connections at the fuel injector. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Test the ignition voltage circuit of the fuel injector for an open between the fuel injector and the splice. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 16 .
Test the control circuit of the fuel injector for a short to voltage, or a short to another circuit. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 16 .
Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 18 . If no, go to step 17 .
Repair the short to ground in the fuel injector control circuit. After repairs, go to step 18 .
Replace the appropriate fuel injector. After repairs, go to step 18 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If yes, go to next step. If no, go to step 2 .
Using scan tool, observe the stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no DTCs are displayed, system is okay.

A cylinder that is misfiring can also cause the misfire current counters to increment for another cylinder. Diagnose the cylinder with the highest level of misfire first.
Performing the Fuel Injector Coil test may help to isolate an intermittent condition. Refer to BASIC FUEL SYSTEM CHECKS in appropriate BASIC DIAGNOSTIC PROCEDURES article.
If the condition is intermittent, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0230: FUEL PUMP PRIMARY CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) provides ignition positive voltage to the coil side of the fuel pump relay. When the ignition switch is first turned ON, the PCM energizes the fuel pump relay, which applies power to the fuel pump. The PCM enables the fuel pump relay as long as the engine is cranking or running, and crankshaft reference pulses are received. If no crankshaft reference pulses are received, the PCM de-energizes the fuel pump relay after 2 seconds. The PCM monitors the voltage on the fuel pump relay control circuit. If the PCM detects an incorrect voltage on the fuel pump relay control circuit, DTC P0230 sets.

The ignition is ON.
The system voltage is 9-18 volts.

The PCM detects an incorrect voltage on the control circuit of the fuel pump relay.
The condition exists for less than 1 second.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 Listen for an audible click when the fuel pump relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
4 This step verifies that the PCM is providing voltage to the fuel pump relay.
5 This step tests for an open in the ground circuit to the fuel pump relay.
6 This step tests if voltage is constantly being applied to the control circuit of the fuel pump relay.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. With a scan tool, command the fuel pump relay ON and OFF. Does the fuel pump relay turn ON and OFF with each command? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close as possible to the Freeze Frame/Failure records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the fuel pump relay. Turn ignition on, with engine off. Probe the control circuit of the fuel pump relay harness connector with a test light connected to a good ground. With a scan tool, command the fuel pump relay ON and OFF. Does the test light turn ON and OFF with each command? If yes, go to next step. If no, go to step 6 .
Connect a test light between the control circuit of the fuel pump relay and the ground circuit of the relay. With a scan tool, command the fuel pump relay ON and OFF. Does the test light turn ON and OFF with each command? If yes, go to step 9 . If no, go to step 11 .
Does the test light remain illuminated with each command? If yes, go to step 8 . If no, go to next step.
Test the control circuit of the fuel pump relay for a short to ground or an open. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
Test the control circuit of the fuel pump relay for a short to voltage. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
Inspect for poor connections at the fuel pump relay. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the harness connectors of the PCM. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Repair the ground circuit of the relay. After repairs, go to step 14 .
Replace the fuel pump relay. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Turn ignition on, with engine off. Using scan tool, observe the stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0300: ENGINE MISFIRE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) uses information from the Ignition Control (IC) module and the Camshaft Position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring the variations in the crankshaft rotation speed for each cylinder the PCM is able to detect individual misfire events. A misfire rate that is high enough can cause the Three-Way Catalytic (TWC) converter to overheat under certain conditions. The Malfunction Indicator Light (MIL) will flash ON and OFF when the conditions for TWC converter overheating are present.

DTCs P0101, P0102, P0103, P0107, P0108, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0336, P0341, P0502, P0503, P1106, P1107, P1114, P1115, P1121, P1122, P1336, P1351, P1352, P1361, P1362, or P1374 are not set.
The engine speed is at least 525 RPM and is no more than 5900 RPM.
The system voltage is 9-18 volts.
The ECT is at least 21°F (-7°C) and is no more than 255°F (125°C).
The throttle angle is steady.

The PCM is detecting a crankshaft rotation speed variation indicating a misfire rate sufficient to cause emissions levels to exceed the mandated standard.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 Depending on the cause of the misfire, the Misfire History Cyl # counter will display a large number for the misfiring cylinders. Values for the non-misfiring cylinders will be less than 1/2 as great as the misfiring cylinders. When investigating a misfire, always start with items associated with the cylinders that have the largest number of counts stored in the Misfire History Cyl # counter.
5 If the misfiring cylinders are companion cylinders, the condition is most likely linked to the ignition system.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Are any other DTCs set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Start and idle the engine. Review and record scan tool Freeze Frame data. Operate the vehicle to duplicate the conditions present when the DTC was set, as defined by the Freeze Frame data. Monitor the scan tool Misfire Current Cyl # display for each cylinder. Is Misfire Current # display incrementing for any cylinder, indicating a misfire currently occurring? If yes, go to step 5 . If no, go to next step.
View the Misfire History Cyl # display on the scan tool. Does Misfire History Cyl # display a very large value for more than one cylinder? If yes, go to next step. If no, go to step 8 .
Are the misfire values displayed on the Misfire History Cyl # related to companion cylinders (i.e., 1/4, 2/5, 3/6)? If yes, go to step 9 . If no, go to next step.
Inspect the following items: Excessive vibration from sources other than the engine. The following are possible sources of vibration: The drive belts, variations in brake rotor thickness, vacuum hoses, crankcase ventilation system for vacuum leaks, throttle body and intake manifold for vacuum leaks, PCM grounds and spark plug wires. Measure the resistance of the spark plug wires associated with the misfiring cylinders. Check EGR valve to exhaust manifold gasket for signs of leaks or damage. Check fuel for contamination. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Install a fuel pressure gauge. Turn ignition on, with engine off. With a scan tool, command the fuel pump ON. Monitor the fuel pressure with the fuel pump running. Does the fuel pressure gauge indicate that the fuel pressure is within 52-59 psi (358-405 kPa). If yes, go to next step. If no, diagnose fuel system.
Test for proper fuel injector operation. Refer to FUEL INJECTOR BALANCE TEST under FUEL SYSTEMS in appropriate SYSTEM & COMPONENT TESTING article. Did you find and correct the condition? go to step 18 . If no, go to next step.
Inspect the ignition wires and coils associated with the misfiring cylinders for the following conditions: Carbon tracking/arching and damage, spark plug wires connected to incorrect cylinders at coil and spark plug, or poor terminal connections at coil and spark plug. If a problem is found, repair as necessary. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Install the J-26792 Spark Tester at the spark plug end of the ignition wire associated with the misfiring cylinders. Jumper the spark plug end of the companion cylinder ignition wire to engine ground. The companion cylinder is the cylinder that shares the same ignition coil (i.e., 1/4, 2/5, 3/6). Crank the engine while observing the spark tester. Is spark present? If yes, go to step 15 . If no, go to next step.
Measure the resistance of the ignition wires associated with the cylinders that were indicated as misfiring. Replace the ignition wires if the resistance measures more than 3000 ohms per foot. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Measure the resistance of the secondary ignition coils associated with the misfiring cylinders. If the resistance is not 5-8 k/ohms, replace the malfunctioning ignition coils. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Remove the ignition coils associated with the misfiring cylinders. Inspect the coils for signs of carbon tracking, cracks or other damage. Did you find and correct the condition? If yes, go to step 18 . If no, go to next step.
Leave the ignition coils disconnected. Connect a test light across the ignition module primary circuit terminals. Remove the fuel injector fuse. Observe the test light while cranking the engine. Does the test light blink? If yes, go to step 16 . If no, go to step 17 .
Remove the spark plugs from the cylinders associated with the misfire. Inspect the spark plugs. Did you find and correct the condition? If yes, go to step 18 . If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Replace the ignition coils associated with the misfiring cylinders. After repairs, go to step 18 .
Replace the ignition control module. After repairs, go to next step.
Review and record Freeze Frame data. Clear DTCs. Start and idle the engine. Operate vehicle to duplicate the conditions present when the DTC was set, as defined by the Freeze Frame data. Monitor the scan tool Misfire Current Cyl # display for each cylinder. Is Misfire Current Cyl # display incrementing for any cylinder, indicating a misfire currently occurring? If yes, diagnose for an engine mechanical problem. If no, system is okay.

The scan tool will indicate if a test has failed since the codes have been cleared. Misfire history will be stored and displayed for each of the cylinders at the time of the failure.
The CKP system variation learn procedure must be performed if any of the following conditions are true: The PCM has been replaced, DTC P1336 is set, engine has been replaced, crankshaft has been replaced, crankshaft balancer has been replaced or the CKP sensor has been replaced.
If the condition is intermittent, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0325: KNOCK SENSOR MODULE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Knock Sensor (KS) produces an alternating current voltage at all engine speeds and loads. The Powertrain Control Module (PCM) then adjusts the spark timing based on the amplitude and on the frequency of the KS signal. The PCM uses the KS signal in order to calculate the average voltage and assigns a voltage value. The PCM inspects the KS and the related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should remain out of the assigned voltage range. This DTC will set if the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system.

DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0336, P0341, P0502, P0503, P1114, P1115, P1121, P1122, or P1336 are not set.
The engine speed is 1000-5000 RPM.
The throttle angle is more than 15 percent.
The engine load is more than 45 percent.
The ECT is more than 140°F (60°C).
The maximum spark retard is less than 15 degrees.
The system voltage is more than 9 volts.
The engine run time is more than 30 seconds.

The PCM detects a malfunction in the KS diagnostic circuitry which will not allow proper diagnosis of the KS circuit.
Condition exists for at least 1 second.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or within the observed parameters of the Freeze Frame/Failure Records. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running in the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Did the DTC Run and Pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does scan tool displays any undiagnosed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0327: KS CIRCUIT - LOW VOLTAGE (BANK 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Knock Sensor (KS) produces an alternating current voltage at all engine speeds and at loads. The Powertrain Control Module (PCM) adjusts spark timing based on the amplitude and on the frequency of the KS signal. The PCM uses the KS signal in order to calculate the average voltage and assigns a voltage value. The PCM inspects the KS and the related wiring by comparing the actual knock signal to the assigned voltage range. A normal KS signal should stay outside the assigned voltage range. This DTC will set if the KS signal is within the assigned voltage range or if the KS signal is not present.

DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0336, P0341, P0502, P0503, P1114, P1115, P1121, P1122, or P1336 are not set.
The engine speed is 1000-5000 RPM.
The engine has been running for a minimum of 30 seconds.
The throttle angle is more than 15 percent.
The engine load is more than 45 percent.
The ECT is greater than 140°F (60°C).
The maximum spark retard is less than 15 degrees.
The system voltage is more than 9 volts.

The PCM detects a KS signal voltage within the average voltage range for at least 10 seconds and engine run time is more than 30 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

3 This step ensures that the malfunction is present.
5 Tapping on the engine block will simulate an engine knock.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start the engine. Monitor the DTC information using scan tool. Does the scan tool display any other DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running in the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Disconnect the KS harness. Set the Digital Multimeter (DMM) to the 400 k/ohms scale. Measure the resistance of the KS using the DMM connected to a good ground. Is the resistance of the KS about 100 k/ohms? If yes, go to next step. If no, go to step 9 .
With the DMM still connected, set the DMM to the 400 mV alternating current Hertz scale. Tap on the engine block near the KS while observing the signal indicated on the DMM. Is any signal indicated on the DMM while tapping on the engine block near the KS? If yes, go to next step. If no, go to step 9 .
Turn ignition off. Disconnect the PCM harness connector. Test the KS circuit for open, high resistance, short to ground, or short to voltage. Did you find and correct the condition? If yes, go to step 11 . If no, go to next step.
Inspect the KS signal circuit for a bad terminal connection at the KS. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 11 . If no, go to next step.
Inspect the KS signal circuit for a bad terminal connection at the PCM. If a condition is found, repair as necessary. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Replace the KS. After repairs, go to step 11 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does scan tool displays any undiagnosed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

If the KS is dropped, the KS must be replaced. Inspect KS for proper installation. A KS that is loose or over torqued may cause the DTC to set. If condition is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0336: CKP SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The circuit uses 2 different types of Crankshaft Position (CKP) sensors. The CKP sensor "B" is connected directly to the Ignition Control Module (ICM), and consists of the CKP 1 sensor signal circuit and the low reference circuit.

The CKP sensor "A" connects directly to the Powertrain Control Module (PCM), and consists of the 12-volt reference circuit, the medium resolution engine speed signal circuit and the low reference circuit If PCM detects an incorrect number of CKP pulses, DTC P0336 sets.

The engine is running, and the 3X reference pulses have been received for a minimum of 3 seconds.

The ratio of 24X reference pulses to 3X reference pulses received by the PCM is incorrect.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 If you were sent here from DTC P0341, proceed with DTC P0336 Diagnostic even if DTC P0336 has not failed this ignition.
8 The 24X RPM on the scan tool should change each time the medium resolution engine speed signal circuit is touched.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Start the engine. Observe the 24X parameter with a scan tool. Does 24X RPM vary with engine speed up to about 1600 RPM? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off. Start the engine. Operate the vehicle within the conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC fail this ignition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the CKP sensor "A" connector. Turn ignition on, with engine off. Measure the voltage from the 12-volt reference circuit of the CKP sensor "A" to a good ground with the DMM. Does the voltage measure about B+? If yes, go to step 6 . If no, go to next step.
Test the 12-volt reference circuit of the CKP sensor "A" for a short to ground or for an open. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 12 .
Connect a test light to battery positive voltage. Touch the CKP sensor "A" low reference circuit. Does test light illuminate? If yes, go to step 8 . If no, go to next step.
Test the low reference circuit of the CKP sensor "A" for an open. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 12 .
Observe the 24X RPM with a scan tool. Connect a 5-amp fused jumper wire to battery positive voltage, momentarily touch the medium resolution engine speed signal circuit 5 times for a duration of 1 second each. Does 24X RPM change each time the signal circuit is touched? If yes, go to step 13 . If no, go to next step.
Did the fuse in the jumper wire open? If yes, go to step 11 . If no, go to next step.
Test the medium resolution engine speed signal circuit of the CKP sensor "A" for a short to voltage or for an open. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 12 .
Test the medium resolution engine speed signal circuit of the CKP sensor "A" for a short to ground. Did you find and correct the condition? If yes, go to step 16 . If no, go to next step.
Test for an intermittent or for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 14 .
Test for an intermittent or for a poor connection at the 24X CKP sensor. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 15 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Replace CKP sensor "A". After repairs, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step 2 . If no, go to next step.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

DTC P0336 can be caused by secondary components leaking high voltage into the ICM. Inspect for the following conditions

Incorrect harness routing near the secondary ignition components.
Ignition coil arcing to wiring harness or IC module Inspect ignition coils for cracks, for carbon tracking, or for other signs of damage.
Secondary ignition wires arcing to the wiring harness.
If the DTC is determined to be intermittent, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0341: CMP SENSOR CIRCUIT PERFORMANCE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

During cranking, the Ignition Control (IC) module monitors the 7X Crankshaft Position (CKP) sensor signal. Once the engine starts, the IC module determines spark synchronization by the Camshaft Position (CMP) sensor pulses. The Powertrain Control Module (PCM) constantly monitors the number of pulses on the CMP signal circuit and compares the number of CMP pulses to the number of 24X reference pulses and the number of 3X reference pulses being received. If the PCM receives an incorrect number of pulses on the CMP signal circuit, DTC P0341 will set.

The engine is running.

The CMP sensor reference pulse is not detected during every engine revolution.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Attempt to start the engine. Does the engine start and run? If yes, go to next step. If no, go to step 4 .
Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . You may operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the Camshaft Position (CMP) sensor connector. Turn ignition on, with engine off. Probe the 12-volt reference circuit of the CMP sensor harness connector with a test light that is connected to a good ground. Does the test light illuminate? If yes, go to step 6 . If no, go to next step.
Probe the 12-volt reference circuit of the CMP sensor harness connector with a test light that is connected to battery voltage. Does the test light illuminate? If yes, go to step 12 . If no, go to step 11 .
Probe the low reference circuit of the CMP sensor harness connector with a test light that is connected to battery voltage. Does the test light illuminate? If yes, go to next step. If no, go to step 13 .
Jumper the 12-volt reference circuit from the CMP sensor to the CMP sensor harness connector. Jumper the low reference circuit from the CMP sensor to the CMP sensor harness connector. Measure the Frequency from the CMP sensor signal circuit of the CMP sensor to a good ground with a DMM set to the DC voltage scale. Crank the engine. Does the Frequency measure within 1-3 Hz? If yes, go to next step. If no, go to step 16 .
Disconnect PCM. Measure the resistance of the CMP sensor signal circuit from the CMP sensor harness connector to the PCM harness connector with a DMM. Does the resistance measure more than 5 ohms? If yes, go to step 18 . If no, go to next step.
Connect the PCM connector. Probe the signal circuit of the CMP sensor harness connector with a test light connected to battery voltage. Does the test light illuminate? If yes, go to step 14 . If no, go to next step.
Probe the signal circuit of the CMP sensor harness connector with a test light connected to a good ground. Does the test light illuminate? If yes, go to step 15 . If no, go to step 17 .
Test the CMP 12-volt reference circuit between the CMP sensor and PCM for an open or high resistance. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 17 .
Test the CMP 12-volt reference circuit between the CMP sensor and the PCM for a short to ground. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 20 .
Test the CMP low reference circuit between the CMP sensor and the PCM for an open or high resistance. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 17 .
Test the CMP signal circuit between the CMP sensor and the PCM for a short to ground. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 20 .
Test the CMP signal circuit between the CMP sensor and the PCM for a short to voltage. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 20 .
Test for an intermittent and for poor connections at the CMP harness connector. If you find a poor connection, repair the connector as necessary. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 19 .
Test for an intermittent and for poor connections at the PCM harness connector. If you find a poor connection, repair the connector as necessary. Did you find and correct the condition? If yes, go to step 21 . If no, go to step 20 .
Repair the CMP signal circuit between the CMP sensor and the PCM for an open or high resistance. After repairs, go to step 21 .
Replace CMP sensor. After repairs, go to step 21 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition? If yes, go to step 2 . If no, go to next step.
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

DTC P0401: EGR SYSTEM

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) tests the Exhaust Gas Recirculation (EGR) system during deceleration by momentarily commanding the EGR valve to open while monitoring the Manifold Absolute Pressure (MAP) sensor signal. When the EGR valve is opened, the PCM should see a proportional increase in MAP. If the expected increase in MAP is not seen, the PCM notes the amount of error that was detected and adjusts an internal fail counter towards a fail threshold level. When the fail counter exceeds the fail threshold level, the PCM will set this DTC. The number of test samples required to accomplish this may vary according to the amount of detected flow error.

Normally, the PCM will only allow 1 EGR flow test sample to be taken during an ignition cycle. In order to aid in verifying a repair, the PCM allows 12 test samples during the first ignition cycle following a scan tool Clear Info or a battery disconnect. Between 9-12 samples should be sufficient for the PCM to determine adequate EGR flow and pass the EGR test.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0201-P0206, P0300, P0336, P0403, P0404, P0405, P0502, P0503, P0506, P0507, P1106, P1107, P1111, P1112, P1114, P1115, P1121, P1122, P1374, or P1404 are not set.
The system voltage is 10-18 volts.
The AC status does not change.
The transaxle range does not change.
The TP angle is less than 1 percent, deceleration.
The IAT is more than 176°F (80°C).
The ECT is more than 167°F (75°C).
The engine speed is 1050-1300 RPM.
The IAC position is steady.
The MAP is steady between 15-70 kPa.
The vehicle speed is more than 35 MPH during deceleration.
The BARO sensor less than 70 kPa.
The vehicle will need to be driven at greater than 50 MPH, and then allowed to decelerate. When the vehicle is decelerating while meeting all of the criteria listed above, the PCM will enable the test to run. When the test is running, you will see the desired EGR parameter and the EGR position sensor on the scan tool change from 0 to a calibrated value greater than 0.

The MAP changes monitored during EGR flow test indicate insufficient EGR flow.

The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This DTC is set when the PCM does not detect a predetermined change in MAP when the EGR valve is commanded. This step inspects for any MAP sensor DTCs. A malfunctioning MAP sensor may cause this DTC to set.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Are there any MAP DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Inspect the exhaust system for modification of original installed parts or leaks. Repair the exhaust system as necessary if you locate a problem. Did you find and correct the condition? If yes, go to step 7 . If no, go to next step.
Inspect the EGR valve gasket and pipe for leaks. If you locate a problem, clean or replace the EGR system components as necessary. Did you find and correct the condition? If yes, go to step 7 . If no, go to next step.
Remove the EGR valve. Inspect the following components for leaks and restrictions: The EGR pintle and EGR valve passages. Did you find and correct the condition? If yes, go to step 7 . If no, go to next step.
Remove the EGR inlet pipe from the exhaust manifold. Inspect the manifold EGR ports and the EGR inlet pipe for a blockage caused by excessive deposits or other damage. Did you find and correct the condition? If yes, go to next step. If no, «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

Vacuum restriction to the MAP sensor. A restriction to MAP sensor can cause EGR flow test to fail due to insufficient MAP changes being monitored during the test. Inspect for objects blocking the vacuum to MAP sensor.
An engine that is running poorly may cause this DTC to set.
Poor connection or damaged harness. Inspect wiring harness for damage.
If the harness appears to be okay, observe the EGR position sensor display on the scan tool while moving the connectors and the wiring harnesses that are related to the EGR valve. A change in the display indicates the location of the malfunction.

In order to verify a repair, clear info with the scan tool and run the EGR flow test, keeping the following conditions in mind

The PCM will only run the EGR flow test during a gradual deceleration.
The PCM will only run the EGR test during a closed throttle condition.
The PCM will only run the EGR test at vehicle speeds greater than 35 MPH.
Several deceleration cycles, typically 9-12, will be necessary in order to run a sufficient number of EGR flow test samples.
The EGR Test Counter displayed on the scan tool can be useful in determining that the EGR flow test is running, and to track the number of test samples taken. The counter will increment each time a test sample is taken.

DTC P0403: EGR SOLENOID CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. The linear EGR valve is controlled by using an ignition positive driver and ground circuit within the PCM. The driver has the ability to detect an electrical malfunction in the ignition positive or ground circuit. If an electrical malfunction occurs, the driver signals the PCM to set this DTC.

The engine is cranking or running.
System voltage is 9-18 volts.

The PCM detects an electrical malfunction in the EGR high control circuit or in the EGR low control circuit.
The condition is present for more than 20 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 When using the scan tool to increment the EGR valve, increment the valve to 10 percent then to 0 percent. Repeat this process to see if test light turns ON then OFF. If the test light stays ON after commanded to 0 percent, the EGR solenoid high control circuit is shorted to voltage.
5 This step tests for an open in the ground circuit to the solenoid.
6 This step tests if voltage is constantly being applied to the solenoid.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. Command the EGR from 0-100 percent with a scan tool. Does the EGR position sensor remain close to the Desired EGR Position at all commanded positions? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close as possible to the Freeze Frame/Failure Records that you observe. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the EGR. Turn ignition on, with engine off. Probe the EGR valve high control circuit with a test light connected to a good ground. Command the EGR between 0-10 percent with a scan tool. Does the test light turn ON and OFF with each command? If yes, go to next step. If no, go to step 6 .
Connect a test light between the EGR valve high control circuit and the EGR valve low control circuit. Command the EGR between 0-10 percent with a scan tool. Does the test light turn ON and OFF with each command? If yes, go to step 10 . If no, go to step 9 .
Does the test light remain illuminated with each command? If yes, go to step 8 . If no, go to next step.
Test the EGR valve high control circuit for a short to ground or for an open. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Test the EGR valve high control circuit for a short to voltage. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Test the EGR valve low control circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 11 .
Inspect for poor connections at the harness connector of the EGR. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at PCM harness connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the EGR. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

DTC P0404: EGR SYSTEM

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM. The PCM compares the EGR position sensor with desired EGR position when the valve is commanded open. If the difference between the EGR position sensor and desired EGR position is more than 15 percent this DTC will set.

The ignition voltage is greater than 11 volts.
The EGR valve is commanded to open.

The difference between the EGR position sensor and the desired EGR position is more than 15 percent.
The condition is present for more than 20 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step verifies that the malfunction is present.
3 If DTC P0404 will only set during certain conditions, the malfunction may be intermittent. Refer to Diagnostic Aids. If an intermittent wiring problem is not present, test for a faulty connection at the PCM or the EGR valve. If the connections are okay, and if DTC P0404 continues to set, replace the EGR valve.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. With a scan tool, command the EGR valve from 0 to 100 percent. Does the EGR position sensor remain within 15 percent of the Desired EGR Position at all commanded positions? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the EGR valve. Turn ignition on, with engine off. With a scan tool, observe the EGR position sensor parameter. Does the scan tool indicate that the EGR position sensor is at 0 percent? If yes, go to next step. If no, go to step 8 .
Measure the voltage from the 5-volt reference circuit of the EGR position sensor to the low reference circuit of the EGR position sensor. Does the Digital Multimeter (DMM) display voltage about 5 volts? If yes, go to next step. If no, go to step 7 .
Connect a fused jumper between the 5-volt reference circuit of the EGR position sensor and the EGR valve position signal circuit of the EGR position sensor. Does the scan tool indicate that the EGR position sensor is about 100 percent? If yes, go to step 12 . If no, go to step 10
Measure the voltage from the 5-volt reference circuit of the EGR position sensor to a good ground. Does the DMM display voltage about 5 volts? If yes, go to step 9 . If no, go to step 11 .
Test the EGR valve position signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 13 .
Test the low reference circuit for an open or high resistance. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 13 .
Test the EGR valve position signal circuit for high resistance or a high resistance short to ground. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 13 .
Test the 5-volt reference circuit of the EGR position sensor for an open, a short to ground, or a short to voltage. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 13 .
Inspect for poor connections at the harness connector of the EGR valve. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 14 .
Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 16 . If no, go to step 15 .
Replace the EGR valve. After repairs, go to step 16 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

Check for excessive deposits on the EGR pintle or seat. Remove the EGR valve and inspect for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick. If problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0405: EGR SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) valve pintle position input to ensure that the valve responds properly to commands from the PCM and to detect a fault if the EGR position sensor circuit is open or shorted. If the PCM detect an excessively low EGR position sensor signal voltage, this DTC will set.

The ignition voltage is greater than 11 volts.

The EGR position sensor is less than 0.35 volt at any time and condition is present for more than 20 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step verifies that the malfunction is present.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. Observe the Exhaust Gas Recirculation (EGR) position sensor voltage parameter with a scan tool. Does the scan tool indicate that the EGR position sensor voltage is less than 0.35 volt? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records that you observe. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the EGR valve. Connect a fused jumper wire between the 5-volt reference circuit of the EGR position sensor and the EGR valve position signal circuit of the EGR position sensor. Turn ignition on, with engine off. Observe the EGR position sensor parameter with a scan tool. Does the scan tool indicate that the EGR position sensor is about 100 percent? If yes, go to step 10 . If no, go to next step.
Disconnect the fused jumper wire. Measure the voltage from the 5-volt reference circuit of the EGR position sensor to the low reference circuit of the EGR position sensor. Does the Digital Multimeter (DMM) display voltage about 5 volts? If yes, go to step 9 . If no, go to next step.
Test the 5-volt reference circuit of the EGR position sensor for an open or high resistance. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
Test all 5-volt reference circuits for a short to ground. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
With a DMM connected between the EGR position sensor 5-volt reference circuit and the EGR position sensor ground circuit, observe voltage while disconnecting all sensors, one at a time, that use a 5-volt reference signal. A change in voltage indicates the faulty component. Replace that component as necessary. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 11 .
Test the EGR position signal circuit for a short to ground, for high resistance, or for an open. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 11 .
Test the EGR valve position signal circuit for a short to the EGR solenoid high control circuit. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 12 .
Inspect for poor connections at PCM harness connector. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 14 .
Inspect for poor connections at the harness connector of the EGR valve. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
Replace the EGR valve. After repairs, go to step 15 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If yes, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

DTC P0420: TWC SYSTEM LOW EFFICIENCY (BANK 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

In order to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides Of Nitrogen (NOx), a Three-Way Catalytic (TWC) converter is used. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas, converting these chemicals into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx, converting these chemicals to nitrogen. The converter also has the ability to store excess oxygen and release the stored oxygen to promote these reactions. This Oxygen Storage Capacity (OSC) is a measurement of the catalysts ability to control emissions. The Powertrain Control Module (PCM) monitors this process using a Heated Oxygen Sensor (HO2S) located in the exhaust stream past the TWC converter. When the catalyst is functioning properly, the HO2S 2 is slow to respond to a large change in the HO2S 1 signal. When the HO2S 2 responds quickly to a large change in the HO2S 1 signal, the OSC and efficiency of the catalyst is considered to be bad. The Malfunction Indicator Light (MIL) will be illuminated if subsequent tests also indicate a failure.

Meet the conditions for engine warm up. Use the scan tool catalyst data list in order to verify the following conditions: DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0134, P0135, P0137, P0138, P0140, P0141, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0336, P0341, P0401, P0403, P0404, P0405, P0440, P0442, P0443, P0446, P0449, P0502, P0503, P0506, P0507, P1133, P1134, P1336, P1351, P1352, P1361, P1362, P1374, P1404, or P1441 are not set. The engine has been running for more than 10 minutes. The ECT is 158-255°F (70-124°C). The BARO is more than 75 kPa. The vehicle is in Closed Loop. The IAT is -4 to 212°F (-20 to 100°C). The battery voltage is more than 10.7 volts.
Warm the catalyst: Fully open the hood. Place the transmission in Park (A/T) or in Neutral (M/T). Set the park brake. PRESS and HOLD the service brake. Each time the engine is started the diagnostic can run up to 18 times. After the 10 minute run time, and before the diagnostic runs the first time, the engine must run an additional 5 minutes between 1500-2500 RPM. For any additional tests on the same key cycle, the engine must be between 1500-2500 RPM for 1 minute. In order to activate the diagnostic, return to idle and place the vehicle in Drive (A/T), or depress the clutch pedal (M/T).
Test the catalyst: Verify that the transaxle is in Drive (A/T) or is in Neutral with the clutch pedal depressed (M/T). Within 60 seconds, the air fuel ratio will go lean less than 14.1 for up to 7 seconds, and then may go rich, greater than 15.3 for up to 7 seconds. Use the scan tool in order to determine if DTC P0420 has passed or failed this key cycle.

The PCM determines that the catalysts OSC is below a threshold considered acceptable.

The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 If any component DTCs are set, diagnose those DTCs first. A fault in a component can cause the TWC to appear degraded or may have caused the TWC failure.
3 Clearing the DTCs allows the catalyst test to be completed up to 6 times this ignition cycle. If the A/C is not turned OFF the diagnostic will not run. The engine must be warmed-up. The TWC needs to be warmed-up by raising the engine speed greater than idle for the specified time prior to each attempted test. Verify if DTC passed or failed this ignition cycle. If the DTC does not pass or fail look for a possible reason that would cause the test to abort.
4 This step includes tests for conditions that can cause the TWC to appear degraded. Repair any problems found before proceeding with this diagnostic procedure.
9 If the TWC needs to be replaced, ensure that another condition which could damage the TWC is not present. Conditions may include misfire, high engine oil or coolant consumption, retarded spark timing, a weak spark, or a rich or lean fuel system. Correct any possible causes of TWC damage before replacing the converter.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Are there any other DTCs set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Clear DTCs using the scan tool. Turn the A/C OFF. Start the engine and wait until the vehicle is fully warmed up. Fully open the hood. Operate the vehicle within the Conditions for Running this DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Test may need to be completed up to 6 times in order to pass or fail. Does the scan tool indicate the DTC ran and passed this ignition cycle? If yes, system okay. If no, go to next step.
Inspect for dents, severe discoloration caused by excessive temperatures, holes, or internal rattle caused by damaged catalyst substrate. Ensure that the TWC is a correct original equipment manufacturer part. Did your inspection reveal a problem? If yes, go to step 9 . If no, go to next step.
Inspect the exhaust system for leaks. Did your inspection reveal a problem? If yes, go to step 7 . If no, go to next step.
Inspect oxygen sensors for damage or oxygen sensor wiring harness for damage. Was a repair necessary? If yes, go to step 8 . If no, go to step 9 .
Repair exhaust system as necessary. After repairs, go to step 10 .
Repair HO2S and wiring as necessary. After repairs, go to step 10 .
Replace catalytic converter. After repairs, go to next step.
Clear DTCs using the scan tool. Turn the A/C OFF. Start the engine and wait until the vehicle is fully warmed up. Fully open hood. Operate the vehicle within the Conditions for Running this DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Test may need to be completed up to 6 times in order to pass or fail. Does the scan tool indicate the DTC ran and passed this ignition cycle? If yes, go to next step. If no, go to step 4 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

The PCM will not enable the catalyst test until following conditions are met: The engine speed is within 200 RPM of the desired idle. The TP is 1.5 percent or less. The short term FT is -20 to 20 percent.
The catalyst test will abort if the vehicle falls outside the conditions listed below while the test is running: The engine speed is within 200 RPM of the desired idle. The throttle position is 1.5 percent or less. The short term FT is -20 to 20 percent.
The catalyst test will abort if the vehicle falls outside the conditions listed below while the test is running: The engine speed is within 200 RPM of the desired idle. The throttle position is 1.5 percent or less. The short term FT is -20 to 20 percent.
The catalyst test may abort due to a change in the engine load. If this condition occurs, use the scan tool in order to force the cooling fans ON. Return to step 3 in the test procedure. NOTE: When using the scan tool in order to force the cooling fans ON, use the next list and previous list soft keys in order to enter the catalyst data list. If the catalyst data list is not entered this way the cooling fan control will be canceled.
The number of attempted tests is limited to 18 per key cycle.
More than 6 tests may have to be attempted in order to get 6 completed tests. An aborted test counts as an attempted test.
If 18 tests have been attempted and if a decision has not been made during this key cycle, turn the key OFF for 30 seconds. Start the vehicle, and perform the conditions for running the DTC, including the 10 minute run time.
After returning to an idle the HO2S 1 signal may stay rich or lean for several seconds, causing the test to be delayed.
If the condition is determined to be intermittent, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0440: EVAP SYSTEM

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The control module tests the Evaporative Emission (EVAP) system for a large leak. The control module monitors the Fuel Tank Pressure (FTP) sensor signal to determine the EVAP system vacuum level. When the conditions for running are met, the control module commands the EVAP canister purge valve OPEN and the EVAP vent valve CLOSED. This allows engine vacuum to enter the EVAP system. At a calibrated time, or vacuum level, the control module commands the EVAP canister purge valve closed, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum level. If the system is unable to achieve the calibrated vacuum level, or the vacuum level decreases too rapidly, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves. See EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP table.

Control Module Command	EVAP Canister Purge Valve	EVAP Canister Vent Valve
ON	Open	Closed
OFF	Closed	Open

EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP

DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121, or P1122 are not set.
The ignition voltage is 10-18 volts.
The BARO is more than 75 kPa.
The fuel level is 15-85 percent.
The ECT is 39-86°F (4-30°C).
The IAT is 39-86°F (4-30°C).
The start-up ECT and IAT are within 16°F (9°C).
The VSS is less than 75 MPH.

The EVAP system is not able to achieve or maintain vacuum during the diagnostic test.

The control module will illuminate the Malfunction Indicator Light (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
The control module will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

The control module will turn the MIL OFF during the first trip in which the diagnostic has been run and passed.
A last test failed (current DTC) clears when the control module turns OFF the MIL.
The history DTC will clear after the control module runs and passes 40 consecutive warm up cycles with no failure.
The DTC can be cleared by using a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 This step is used to verify if a leak is present.
6 This step verifies proper operation of the FTP sensor.
9 This step tests the EVAP canister purge valve for a restriction or blockage.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Does the scan tool indicate DTC P0443 or DTC P0449 are also set? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Inspect the EVAP system for loose, missing, or damaged service port Schrader valve. For loose, incorrect, missing or damaged fuel fill cap, or a damaged EVAP canister purge valve. Raise vehicle on a hoist. Inspect EVAP system for disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses, a damaged EVAP canister vent valve or EVAP canister. Did you find and correct the condition? If yes, go to step 19 . If no, go to next step.
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to next step.
Install the J-41415-40 Fuel Tank Cap Adaptor. Connect the J-41413 EVAP Pressure and Purge Station and the vehicle fuel fill cap to the fuel tank cap adaptor. Turn ignition on, with engine off. Seal the EVAP system with scan tool. Pressurize the system to 5 in. H2O with the J-41413. Rotate the J-41413 rotary switch to the OFF/HOLD position. Monitor the pressure gauge for 1 minute. Did you obtain and hold the pressure? If yes, go to next step. If no, go to step 8 .
Compare the EVAP Pressure and Purge Station value to the scan tool Fuel Tank Pressure (FTP) sensor value. Does the value measure near the scan tool value? If yes, go to next step. If no, go to step 12 .
Monitor the pressure gauge on the J-41413. Disconnect the EVAP purge pipe from the EVAP purge valve. Does the EVAP system pressure decrease? If yes, go to step 9 . If no, go to step 10 .
Continuously pressurize the EVAP system with the J-41413. The fuel tank may need to be partially lowered to inspect components located in the upper portion of the tank. Inspect for leaks using J-41416 Ultrasonic Leak Detector at the EVAP system purge pipe, EVAP vapor pipe, EVAP vent hose/pipe, fuel fill pipe/hose, fuel fill cap, EVAP canister, EVAP canister vent valve, EVAP canister purge valve, fuel sender assembly and/or seal, FTP sensor seal, fill limiter vent valve, pressure relief valve, rollover valves, and/or fuel tank. Did you find and repair a leak? If yes, go to step 19 . If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Attach a vacuum gauge to the purge pipe port of the EVAP purge valve. Start the engine and allow the engine to idle. Command the EVAP purge valve to 50 percent with a scan tool. Does the vacuum gauge show vacuum more than 10 in. H2O. If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to step 13 .
Monitor the pressure gauge on the J-41413. Disconnect the purge pipe at the EVAP canister. Does the EVAP system pressure decrease? If yes, go to step 15 . If no, go to next step.
Monitor the pressure gauge on the J-41413. Disconnect the EVAP vapor line from the EVAP canister. Does the EVAP system pressure decrease? If yes, go to step 18 . If no, go to step 14 .
Monitor the FTP sensor voltage with a scan tool. Is the FTP sensor voltage more than 4.3 volts? If yes, go to «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0453-fuel-tank-pressure-sensor) . If no, go to step 16 .
Inspect the vacuum source to the EVAP purge valve for blockage, cuts, or disconnects. Repair as necessary. Did you find and correct the condition? If yes, go to step 19 . If no, go to step 17 .
Repair the pinched or obstructed EVAP vapor pipe. After repairs, go to step 19 .
Repair the restriction in the EVAP purge pipe. After repairs, go to step 19 .
Replace the FTP sensor. After repairs, go to step 19 .
Replace the EVAP purge valve. After repairs, go to step 19 .
Replace the EVAP canister. After repairs, go to next step.
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, go to next step. If no, go to step 5 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Use the J-41413 EVAP Pressure and Purge Station in order to pressurize the EVAP system to aid in locating intermittent leaks. Move all EVAP components while testing with the J-41416 Ultrasonic Leak Detector.
A temporary blockage in the EVAP canister purge valve, purge pipe or EVAP canister could cause an intermittent condition.
Reviewing the Failure Records vehicle mileage since the diagnostic test last failed may help determine how often the condition that caused the DTC to be set occurs. This may assist in diagnosing the condition.

DTC P0442: EVAP SYSTEM - LEAK DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

This DTC tests the Evaporative Emission (EVAP) system for a small leak. The control module monitors the Fuel Tank Pressure (FTP) sensor signal to determine the vacuum decay rate. At an appropriate time, the control module turns the EVAP canister purge valve ON and the EVAP vent valve ON. This allows the engine to draw a vacuum on the EVAP system. At a calibrated time, or vacuum level, the control module turns the EVAP canister purge valve OFF, sealing the system, and monitors the FTP sensor input in order to determine the EVAP system vacuum decay. If the control module detects a leak larger than a calibrated amount, this DTC sets.

The EVAP Canister Purge & Vent Valve Relationship table illustrates the relationship between the ON and OFF states, and OPEN or CLOSED states of EVAP canister purge and vent valves. See EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP table.

DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121, or P1122 are not set.
The ignition voltage is 10-18 volts.
The BARO is more than 75 kPa.
The fuel level is 15-80 percent.
The ECT is 39-86°F (4-30°C).
The IAT is 39-86°F (4-30°C).
The start-up ECT and IAT are within 16°F (9°C).
The VSS is less than 75 MPH.

The EVAP system can achieve vacuum, but a vacuum decay is detected during the diagnostic test.

The control module illuminates the Malfunction Indicator Light (MIL) when the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame/Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 This step verifies that a leak is present.
5 This step verifies that repairs are complete and that there are no other leaks in the system.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Does the scan tool indicate DTCs P0443, P0449, P0452, or P0453 are also set? If yes, diagnose affected DTC(s). See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Inspect the EVAP system for a loose, missing, or damaged service port Schrader valve. Check for loose, incorrect, missing or damaged fuel fill cap. Check for damaged EVAP canister purge valve. Raise vehicle on a hoist. Inspect EVAP system for disconnected, improperly routed, kinked, or damaged EVAP pipes and hoses, damaged EVAP canister vent valve or EVAP canister. Did you find and correct the condition? If yes, go to step 5 . If no, go to next step.
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to next step.
Install the J-41415-40 Fuel Fill Cap Adaptor. Connect the J-41413 EVAP Pressure and Purge Station and the vehicle fuel fill cap to the J-41415-40. Turn ignition on, with engine off. Seal the EVAP system with the scan tool. Continuously pressurize the EVAP system to 15 in. H2O with the J-41413 (fuel tank may need to be partially lowered to inspect components located in upper portion of tank). Using an Ultrasonic Leak Detector, check for leaks in EVAP system purge pipe, vapor pipe, vent hose, fuel fill pipe/hose and fuel fill cap. Check for leaks in the fuel pump assembly and/or seal, FTP sensor seal, fill limiter vent valve, pressure relief valve, rollover valves, permanent EVAP pipes and/or fuel tank. Did you find and correct the condition? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, go to next step. If no, repeat step 5 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. To aid in locating intermittent leaks, use the J-41413 EVAP Pressure and Purge Station to pressurize the EVAP system. Move all EVAP components while testing with the J-41416 Ultrasonic Leak Detector.

DTC P0443: EVAP PURGE SOLENOID CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

An ignition voltage is supplied directly to the Evaporative Emission (EVAP) purge valve. The EVAP purge valve is Pulse Width Modulated (PWM). The control module controls the EVAP purge valve ON time by grounding the control circuit via an internal switch called a driver. The scan tool displays the amount of ON time as a percentage. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the drive, DTC P0443 sets.

The engine speed is more than 400 RPM.
The system voltage is 6-18 volts.

The control module detects that the commanded state of the driver and the actual state of the control circuit Do NOT match.
The above condition is present for a minimum of 5 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step tests if the concern is active. The EVAP purge valve is Pulse Width Modulated (PWM). Clicking should be heard or felt when the purge valve is commanded to 50 percent and should stop when the EVAP purge valve is commanded to 0 percent. The rate at which the valve cycles should increase as the commanded state is increased and decreased as the commanded state is decreased. Repeat the commands as necessary.
5 This step tests if a ground is constantly being applied to the EVAP purge valve.
6 This step verifies that the control module is providing ground to the EVAP purge valve.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. With a scan tool, command the EVAP purge valve to 50 percent and then to 0 percent. Do you hear or feel a clicking from the EVAP purge valve when the valve is commanded to 50 percent? If yes, go to next step. If no, go to step 4 .
Review the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the EVAP purge valve harness connector. Turn ignition on, with engine off. Probe the ignition voltage circuit at the EVAP purge valve harness connector with a test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step 11 .
Connect a test light between the control circuit and the ignition voltage circuit of the EVAP purge valve harness connector. With a scan tool, command the EVAP purge valve to 0 percent. Does the test light illuminate? If yes, go to step 8 . If no, go to next step.
With a scan tool, command the EVAP purge to 50 percent. Does the test light illuminate or pulse when the EVAP purge valve is commanded to 50 percent? If yes, go to step 9 . If no, go to next step.
Test the control circuit of the EVAP purge valve for an open or short to voltage. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
Test the control circuit of the EVAP purge valve for a short to ground. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Inspect for poor connections at the harness connector of the EVAP purge valve. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the harness connector of the control module. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Repair the ignition voltage circuit of the EVAP purge valve. After repairs, go to step 14
Replace the EVAP purge valve. After repairs, go to step 14
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

DTC P0446: EVAP CANISTER VENT BLOCKED

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

This DTC tests the Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge valve ON and the EVAP canister vent valve ON. This allows a vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge valve OFF and the EVAP canister vent valve OFF. The control module monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near 0 in. H2O in a calibrated time, this DTC sets.

The EVAP Canister Purge & Vent Valve Relationship table illustrates the relationship between the ON and OFF states, and the OPEN or CLOSED states of the EVAP canister purge and vent valves. See EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP table.

DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121, or P1122 are not set.
The ignition voltage is 10-18 volts.
The BARO is more than 75 kPa.
The fuel level is 15-85 percent.
The ECT is 39-86°F (4-30°C).
The IAT is 39-86°F (4-30°C).
The start-up ECT and IAT are within 16°F (9°C).
The VSS is less than 75 MPH.

FTP is less than -10 in. H2O.
The condition is present for at least 30 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 This test determines if the fuel tank pressure sensor is functioning.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Did DTC P0443, P0449, P0452 or P0453 set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Inspect the Evaporative Emission (EVAP) system for a damaged EVAP vent valve, or a pinched EVAP vent hose. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to next step.
Disconnect the purge line from the EVAP purge valve. Turn ignition on, with engine off. Observe the Fuel Tank Pressure (FTP) parameter with a scan tool. Does the scan tool indicate FTP about 0 in. H2O. If yes, go to next step. If no, go to step 9 .
Turn ignition off. Reconnect all previously disconnected hardware. Install the J-41415 Fuel Fill Cap Adaptor. Connect the J-41413 EVAP Pressure and Purge Station and the fuel fill cap to the J-41415. Turn ignition on, with engine off. Command the EVAP canister vent valve ON with a scan tool. DO NOT exceed the specified value in this step. Exceeding the specified value may produce incorrect test results. Pressurize the EVAP system to 5 in. H2O with the J-41413. Rotate the J-41413 rotary switch to the OFF/HOLD position. Command the EVAP canister vent valve OFF with a scan tool. Does the scan tool indicate FTP about 0 in. H2O. If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to next step.
Disconnect the EVAP canister vent hose from the EVAP canister vent valve. Does the scan tool indicate FTP within -0.5 to 0.5 in. H2O? If yes, go to step 11 . If no, go to next step.
Disconnect the EVAP vent pipe from the EVAP canister. Does the scan tool indicate FTP about 0 in. H2O? If yes, go to step 14 . If no, go to step 12 .
Observe the FTP sensor voltage with a scan tool. Is the FTP sensor voltage more than 4.3 volts? If yes, go to «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0453-fuel-tank-pressure-sensor) . If no, go to next step.
Test for poor connections at the harness connector of the FTP sensor. Did you find and correct the condition? If yes, go to step 15 . If no, go to step 13 .
Replace the EVAP canister vent valve. When complete, go to step 15 .
Replace the EVAP canister. When complete, go to step 15 .
Replace the FTP sensor. When complete, go to step 15 .
Repair the blockage in the EVAP vent hose. After repairs, go to next step.
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, go to next step. If no, go to step 5 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem. To repair a blockage in the EVAP system.

DTC P0449: EVAP CANISTER VENT SOLENOID CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

An ignition voltage is supplied directly to the Evaporative Emission (EVAP) canister vent valve. The control module controls the EVAP vent valve by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the controlled component. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, DTC P0449 sets.

The engine speed is more than 400 RPM.
The system voltage is 6-18 volts.

The control module detects that the commanded state of the driver and the actual state of the control circuit do not match.
Conditions are present for a minimum of 5 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 Listen or feel for a click when the valve operates. Ensure that both the ON and the OFF states are commanded. Repeat the commands as necessary.
5 This step verifies that the control module is providing ground to the EVAP vent valve.
6 This step tests if the EVAP vent valve control circuit is grounded.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. With the scan tool, command the EVAP vent valve ON and OFF. Do you hear or feel a click from the EVAP vent valve when commanded ON and OFF? If yes, go to next step. If no, go to step 4 .
Review the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observe. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does this DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the EVAP vent valve harness from the vent valve. Turn ignition on, with engine off. Probe the ignition voltage circuit of the EVAP vent valve at the EVAP vent valve harness connector with a test light connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step 11 .
Connect a test light between the control circuit and ignition voltage circuit of the EVAP vent valve at the EVAP vent valve. With a scan tool, command the EVAP vent valve ON and OFF. Does the test light turn ON or OFF with each command? If yes, go to step 9 . If no, go to next step.
Does the test light remain illuminated with each command? If yes, go to step 8 . If no, go to next step.
Test the control circuit of the EVAP vent solenoid for a short to voltage or an open. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
Test the control circuit of the EVAP vent valve for a short to ground. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
Inspect for poor connections at the harness connector of the EVAP vent valve. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the harness connector of the control module. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Repair the ignition voltage circuit of the EVAP vent valve for an open or for a short to ground. Replace the fuse if necessary. After repairs, go to step 14 .
Replace the EVAP vent valve. After repairs, go to step 14 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use a scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0452: FUEL TANK PRESSURE SENSOR CIRCUIT - LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The control module monitors the Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced Evaporative Emission (EVAP) diagnostic. The control module supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases as the FTP decreases (negative pressure or vacuum, high voltage). The FTP sensor signal voltage decreases as the FTP increases, positive pressure, low voltage. When the FTP sensor signal goes below a predetermined value, DTC P0452 will set.

The ignition is ON.

The FTP sensor voltage is less than 0.1 volt.
Condition present for more than 5 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 This step tests for the proper operation of the circuit in the high voltage range.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Idle the engine for 1 minute. Monitor the DTC information using the scan tool. Did DTC P1639 fail this ignition? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
With the scan tool, observe the Fuel Tank Pressure (FTP) sensor voltage. Does the scan tool indicate that the FTP sensor voltage is less than 0.1 volt? If yes, go to step 5 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go next to step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect FTP sensor harness connector. Connect a 3-amp fused jumper wire between the 5-volt reference circuit and signal circuit of the FTP sensor harness connector. Turn ignition on, with engine off. With a scan tool, observe FTP voltage. Does scan tool indicate that the FTP voltage is about 5 volts? If yes, go to step 8 . If no, go to next step.
Test the 5-volt reference circuit of the FTP sensor for a short to ground, for high resistance or open. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Test the signal circuit of the FTP sensor for a short to ground, for high resistance or for an open. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Inspect for poor connections at the harness connector of the FTP sensor. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
Inspect for poor connections at the harness connector of the control module. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Replace the FTP sensor. After repairs, go to step 12 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The control module monitors the Fuel Tank Pressure (FTP) sensor signal in order to detect vacuum decay and excess vacuum during the enhanced Evaporative Emission (EVAP) diagnostic. The control module supplies a 5-volt reference and ground to the sensor. The FTP sensor signal voltage increases as the FTP decreases (negative pressure or vacuum, high voltage). The FTP sensor signal voltage decreases as the FTP increases (positive pressure, low voltage). When the FTP sensor signal goes greater than a predetermined value, DTC P0453 will set.

The ignition is ON.

The FTP sensor signal voltage is greater than 4.9 volt for more than 5 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 If DTC P1639 set, the 5-volt reference circuit may be shorted to a voltage.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Idle the engine for 1 minute. Monitor the DTC Information using the scan tool. Did DTC P1639 fail this ignition? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Turn ignition on, with engine off. With a scan tool, observe the FTP sensor voltage. Is the FTP sensor voltage more than 4.3 volts? If yes, go to step 5 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the FTP sensor harness connector. Turn ignition on, with engine off. With a scan tool, observe the FTP sensor. Does the scan tool indicate that the FTP sensor voltage is greater than 4.3 volts? If yes, go to next step. If no, go to step 7 .
Test the FTP signal circuit for a short to voltage or a short to a 5-volt reference circuit. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 12
Probe the low reference circuit of the FTP sensor with a test light connected to battery voltage. Did the test light illuminate? If yes, go to step 9 . If no, go to next step.
Test the low reference circuit of the FTP sensor for an open. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 10 .
Inspect for poor connections at the harness connector of the FTP sensor. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 11 .
Inspect for poor connections at the harness connector of the control module. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 12 .
Replace the FTP sensor. After repairs, go to step 13
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P0506: IDLE SPEED - LOW

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The engine idle speed is controlled by the Idle Air Control (IAC) valve. The IAC valve is on the throttle body. The IAC valve pintle moves in and out of an idle air passage bore to control air flow around the throttle plate. The valve consists of a movable pintle, driven by a gear attached to a two phase bi-polar permanent magnet electric motor called a stepper motor. The stepper motor is capable of highly accurate rotation, or of movement, called steps. The stepper motor has two separate windings that are called coils. Each coil is fed by two circuits from the Powertrain Control Module (PCM). When the PCM changes polarity of a coil, the stepper motor moves one step. The PCM uses a predetermined number of counts to determine the IAC pintle position. Observe IAC counts with a scan tool. The IAC counts will increment up or down as the PCM attempts to change the IAC valve pintle position. An IAC Reset will occur when the ignition key is turned OFF. First, the PCM will seat the IAC pintle in the idle air passage bore. Second, the PCM will retract the pintle a predetermined number of counts to allow for efficient engine start-up. If the engine idle speed is out of range for a calibrated period of time, an idle speed DTC may set.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0443, P1121, P1404, and P1441 are not set.
The engine run time is more than 2 minutes.
The ECT sensor is more than 158°F (70°C).
The IAT sensor is more than -0.4°F (-18°C).
The BARO sensor is more than 70 kPa.
The ignition voltage is 9-18 volts.
The TP sensor angle is less than 1.5 percent.
The VSS sensor is less than 3 MPH.
The above conditions are met for more than 8 seconds.

The actual engine speed is 100 RPM less than the desired engine speed for more than 8 seconds for each test.
PCM detects the IAC test failed 4 consecutive times per ignition cycle.
The vehicle must enter the above criteria and leave the criteria for 1 second in order to complete one test.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 This test determines the ability of the engine controller and IAC valve circuits to control the IAC valve.
7 This test determines the ability of the PCM to provide the IAC circuits with a ground. On a normal operating system, the test light should not flash while the IAC counts are incrementing.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Set the parking brake and block the drive wheels. Install a scan tool. Start the engine. Turn OFF all accessories. With the scan tool RPM control function slowly increment engine speed to 1700 RPM, then to 600 RPM, then to 1700 RPM. Exit the RPM control function. Does the engine speed stabilize within 100 RPM of the commanded RPM during the above test? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC and within the parameters observed in the Freeze Frame/Failure Records. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the IAC valve. Connect the J-37027-1A IAC Motor Driver to the IAC valve. Start the engine. With the J-37027-1A, command the IAC valve in until near 600 RPM is reached. With the J-37027-1A, command the IAC valve out until near 1700 RPM is reached. Return engine speed to desired idle as indicated on the scan tool data list. Did the engine speed steadily decrease to near 600 RPM and steadily increase to near 1700 RPM when the IAC valve was commanded in and out? If yes, go to next step. If no, go to step 11 .
With a test light connected to ground, probe one of the IAC valve circuits at the IAC valve harness connector using the J-35616-A Connector Test Adaptor Kit. Start the engine. With the J-37027-1A, command low RPM while observing a scan tool until the IAC counts start to increment. With the J-37027-1A, command high RPM while observing a scan tool until the IAC counts start to increment. While the IAC counts are incrementing observe the test light. Return engine idle speed to desired idle as indicated on the scan tool data list. Repeat procedure for the other 3 IAC valve circuits. Did the test light remain ON, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the test? If yes, go to step 10 . If no, go to next step.
Did the test light remain OFF, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the test? If yes, go to step 9 . If no, go to next step.
Connect a test light between the IAC coil "A" low circuit and IAC coil "A" high circuit at the IAC valve harness connector using the J-35616-A. With the J-37027-1A, command low RPM while observing a scan tool until the IAC counts start to increment. With the J-37027-1A, command high RPM while observing a scan tool until the IAC counts start to increment. While the IAC counts are incrementing, observe the test light. Return engine idle speed to desired idle as indicated on the scan tool data list. Repeat procedure with the test light connected between the IAC coil "B" low circuit and the IAC coil "B" high circuit at the IAC valve harness connector. Return engine speed to the desired idle as indicated on the scan tool data list. Did the test light stay illuminated and never flashing while the IAC counts where incrementing during the test? If yes, go to next step. If no, go to step 16 .
Inspect for a poor connection at the IAC valve harness connector. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 12 .
Turn ignition off. Disconnect the PCM harness connectors. With a DMM, test the circuit where the test light remained OFF for an open circuit, a short to ground, or short to another IAC valve circuit. Did you find and correct the condition? If yes, go to step 17 , If no, go to step 12 .
Turn ON the ignition. With a DMM, test the circuit where the test light remained ON for a short to voltage or short to another IAC valve circuit. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 12
Inspect for throttle body damage and tampering, throttle lever screw tampering (if equipped), restricted air intake system (collapsed/clogged air intake duct, before and after the air filter element), restricted air filter element, restriction at throttle body intake screen (if equipped). Remove IAC valve. Inspect for clogged IAC passage, excessive deposits on throttle plate, excessive deposits in throttle bore, or excessive deposits on IAC valve pintle. Repair as necessary. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
Inspect for a poor connection at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 17 . If no, go to next step.
Disconnect the PCM harness connectors With a DMM, test all IAC valve circuits for high resistance. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 16 .
Inspect for a poor connection at the IAC valve harness connector. Did you find and correct the condition? If yes, go to step 17 . If no, go to next step.
Replace the IAC valve. After repairs, go to step 17 .
Turn ignition off. Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. If scan tool displays any undiagnosed DTCs, diagnose affected DTCs. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no other DTCs are displayed, system is okay.

Inspect for the following conditions

High resistance in an IAC circuit.
Restricted air intake system.
Proper operation and installation of all air intake components.
Collapsed, clogged, or loose air intake ducts.
A clogged air filter.
Proper operation of the Mass Air Flow Sensor (MAF), if equipped.
A tampered with or damaged throttle stop screw.
A tampered with or damaged throttle plate, throttle shaft, or throttle linkage.
Objects blocking the IAC passage or throttle bore.
Excessive deposits in the IAC passage or on the IAC pintle.
Excessive deposits in the throttle bore or on the throttle plate.
Vacuum leaks.
A low or unstable idle condition could be caused by a non-IAC system problem that cannot be overcome by the IAC valve.

If the problem is determined to be intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P0507: IDLE SPEED - HIGH

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0171, P0172, P0201, P0202, P0203, P0204, P0205, P0206, P0300, P0401, P0403, P0404, P0405, P0443, P1121, P1404, and P1441 are not set.
The engine run time is more than 2 minutes.
The ECT sensor is more than 158°F (70°C).
The IAT sensor is more than -0.4°F (-18°C).
The BARO sensor is more than 70 kPa.
The ignition voltage is 9-18 volts.
The TP sensor angle is less than 1.5 percent.
The VSS sensor is less than 3 MPH.
The above conditions are met for more than 8 seconds.

The actual engine speed is 150 RPM more than the desired engine speed for more than 8 seconds for each test.
PCM detects the IAC test failed 4 consecutive times per ignition cycle.
The vehicle must enter the above criteria and leave the criteria for 1 second in order to complete one test.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 This test determines the ability of the engine controller and IAC valve circuits to control the IAC valve.
7 This test determines the ability of the PCM to provide the IAC valve circuits with a ground. On a normally operating system, the test light should not flash while the IAC counts are incrementing.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Set the parking brake and block the drive wheels. Install a scan tool. Start the engine. Turn OFF all accessories. With the scan tool RPM control function slowly increment engine speed to 1700 RPM, then to 600 RPM, then to 1700 RPM. Exit the RPM control function. Does the engine speed stabilize within 150 RPM of the commanded RPM during the test? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC and within the parameters observed in the Freeze Frame/Failure Records. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the IAC valve. Connect an J-37027-1A IAC Motor Driver to the IAC valve. Start the engine. With the J-37027-1A, command the IAC valve in until near 600 RPM is reached. With the J-37027-1A, command the IAC valve out until near 1700 RPM is reached. Return engine speed to desired idle as indicated on the scan tool data list. Did the engine speed steadily decrease to near 600 RPM and steadily increase to near 1700 RPM when the IAC valve was commanded in and out? If yes, go to next step. If no, go to step 11 .
With a test light connected to ground, probe one of the IAC valve circuits at the IAC valve harness connector using the J-35616-A Connector Test Adaptor Kit. Start the engine. With the J-37027-1A, command low RPM while observing a scan tool until the IAC counts start to increment. With the J-37027-1A, command high RPM while observing a scan tool until the IAC counts start to increment. While the IAC counts are incrementing observe the test light. Return engine idle speed to desired idle as indicated on the scan tool data list. Repeat this procedure for the other 3 IAC valve circuits. Did the test light remain ON, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the test? If yes, go to step 10 . If no, go to next step.
Did the test light remain OFF, never flashing, while the IAC counts where incrementing at any of the IAC valve circuits during the test? If yes, go to step 9 . If no, go to next step.
Connect a test light between the IAC coil "A" low circuit and IAC coil "A" high circuit at the IAC valve harness connector using the J-35616-A. With the J-37027-1A, command low RPM while observing a scan tool until the IAC counts start to increment. With the J-37027-1A, command high RPM while observing a scan tool until the IAC counts start to increment. While the IAC counts are incrementing, observe the test light. Return engine idle speed to desired idle as indicated on the scan tool data list. Repeat this procedure with the test light connected between the IAC coil "B" low circuit and IAC coil "B" high circuit at the IAC valve harness connector. Return engine speed to the desired idle as indicated on the scan tool data list. Did the test light stay illuminated and never flashing while the IAC counts where incrementing during the test? If yes, go to next step. If no, go to step 16 .
Inspect for a poor connection at the IAC valve harness connector. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 12 .
Turn ignition off. Disconnect the PCM harness connectors. With a DMM, test the circuit where the test light remained OFF for an open circuit, short to ground or short to another IAC valve circuit. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 12 .
Turn ON the ignition. With a DMM, test the circuit where the test light remained ON for a short to voltage or short to another IAC valve circuit. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 12 .
Inspect for throttle body damage and tampering, throttle lever screw tampering (if equipped), vacuum leaks, faulty or incorrectly installed PCV valve and hose (if equipped), throttle shaft binding, throttle linkage or cruise control linkage binding (if equipped). Remove IAC valve and inspect for debris in IAC passage, excessive deposits on throttle plate, throttle bore or on IAC valve pintle. Repair any of the conditions as necessary. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
Inspect for a poor connection at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 17 . If no, go to next step.
Disconnect the PCM harness connectors. With a DMM, test all IAC valve circuits for high resistance. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 16 .
Inspect for a poor connection at the IAC valve harness connector. Did you find and correct the condition? If yes, go to step 17 . If no, go to next step.
Replace the IAC valve. After repairs, go to step 17
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Inspect for the following conditions

High resistance in an IAC circuit.
The correct Positive Crankcase Ventilation (PCV) valve, properly installed and proper operation of the PCV valve.
Proper operation and installation of all air intake components.
Proper installation and operation of the mass air flow sensor, if equipped.
A tampered with or damaged throttle stop screw.
A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped.
A skewed high Throttle Position (TP) sensor.
Excessive deposits in the IAC passage or on the IAC pintle.
Excessive deposits in the throttle bore or on the throttle plate.
Vacuum leaks.
A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve.
If the problem is determined to be intermittent, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 OR P1683: CONTROL MODULE READ ONLY MEMORY

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Note. DTC P0601, P0602 or P1683 may not be applicable on all vehicles.

This diagnostic test applies to internal microprocessor integrity conditions within the control module. This diagnostic test also addresses if the control module is not programmed.

The numbers below refer to the step numbers in the diagnostic procedures.

2 A DTC P0602 indicates the PCM is not programmed.
4 Attempt to program the PCM. If the PCM fails to program a second time, replace the PCM.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is DTC P0602 set? If yes, go to next step. If no, go to step 5 .
Program PCM, see «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. Recheck DTCs. Does DTC P0602 reset? If yes, go to next step. If no, go to next step 6 .
Verify that all tool connections are secure. Verify the programming equipment is operating correctly. Verify the correct software package and the correct calibration package is used. Attempt to program the PCM. Does DTC P0602 reset? If yes, go to next step. If no, go to step 6 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Turn ignition on, with engine off. Use a scan tool in order to clear DTCs. Turn ignition off for 30 seconds. Start the engine. Does the scan tool display any DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
With a scan tool, observe the stored information, Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

For complete details on programming the PCM, see POWERTRAIN CONTROL MODULE under PROGRAMMING.

DTC P0650: MIL CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Ignition voltage is supplied directly to the Malfunction Indicator Light (MIL). The Powertrain Control Module (PCM) controls the light by grounding the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the component being controlled. Each driver has a fault line which is monitored by the PCM. When the PCM is commanding a component on, the voltage of the control circuit should be low, near 0 volts. When the PCM is commanding the control circuit to a component off, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other than what is expected, the fault line status will change causing the DTC to set.

The ignition is ON.

An improper voltage level has been detected on the MIL control circuit.
Condition present for at least 30 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 Command both the ON and the OFF states. Repeat the commands as necessary.
8 If you do not find trouble in the control circuit or the connection at the PCM, the PCM may be faulty. However, this is an extremely unlikely failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ignition on, with engine off. Command the MIL ON and OFF using the scan tool. Does the MIL turn ON and OFF with each command? If yes, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, go to next step.
Turn ignition off. Disconnect the PCM. Turn on the ignition. Is the MIL OFF? If yes, go to next step. If no, go to step 5 .
Probe the MIL control circuit in the PCM harness connector with a fused jumper wire connected to ground. Is the MIL ON? If yes, go to step 6 . If no, go to step 7 .
Repair the short to ground in the MIL control circuit. After repairs, go to step 9 .
Test for poor connections at the PCM. Did you find and correct the condition? If yes, go to step 9 . If no, go to step 8 .
Repair open ignition positive voltage to the MIL bulb or an open or shorted control circuit to battery positive voltage. After repairs, go to step 9 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

If the ignition feed circuit is suspected of being open, inspect the other bulbs which are powered by the same circuit. If the condition is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1106: MAP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure which gives an indication of the engine load. The MAP sensor has a 5-volt reference circuit, and a signal circuit. The Powertrain Control Module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit, and provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to the pressure changes in the manifold. With low manifold absolute pressure such as during idle or deceleration, the PCM should detect a low MAP sensor signal voltage. With high manifold absolute pressure such as ignition ON, with the engine OFF or Wide Open Throttle (WOT), the PCM should detect a high MAP sensor signal voltage. Certain vehicle models will also use the MAP sensor in order to calculate the Barometric Pressure (BARO) when the ignition is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP sensor signal voltage that is intermittently high, DTC P1106 will set.

DTCs P0121, P0122, or P0123 are not set.
The engine has been running for a period of time that is determined by the start-up coolant temperature. The time ranges from 2 minutes at less than -22°F (-30°C) to 1 second at more than 86°F (30°C).
The throttle angle is less than 2 percent when the engine speed is less than 3000 RPM.
The throttle angle is less than 30 percent when the engine speed is more than 3000 RPM.

The MAP sensor voltage is intermittently more than 4.2 volts.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 Many intermittent open or shorted circuits occur with harness/connector movement caused by vibration, by engine torque, and by bumps. This step attempts to recreate this condition.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start the engine. Monitor the DTC information using the scan tool. Does the scan tool display DTC P1635 or P0108 set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Does the scan tool indicate that the MAP sensor voltage is more than 4.2 volts? If yes, go to step 5 . If no, go to next step.
With a scan tool, observe the MAP sensor voltage, while moving the following components: The MAP sensor connector, wiring harness related to MAP sensor, and the PCM connector. Does the scan tool indicate that the MAP sensor voltage is more than 4.2 volts and holding? If yes, go to next step. If no, go to step 11 .
Turn ignition off. Disconnect the MAP sensor electrical connector. Turn ignition on, with engine off. Does the scan tool indicate that the MAP sensor voltage is less than 0.1 volt? If yes, go to next step. If no, go to step 7 .
Disconnect the electrical connector of the Engine Coolant Temperature (ECT) sensor. Connect a test light to B+. Probe the low reference circuit of the MAP sensor with the test light. Does the test light illuminate? If yes, go to step 9 . If no, go to step 8 .
Test the signal circuit of the MAP sensor for a short to voltage. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Test the low reference circuit of the MAP sensor for an open. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Inspect for poor connections at the MAP sensor. Did you find and correct the condition? If yes, go to step 11 . If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Inspect for poor connections at the PCM. Did you find and correct the condition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Inspect the MAP sensor vacuum source for leaks, for restrictions or for poor connections. If an intermittent condition exists, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1107: MAP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Manifold Absolute Pressure (MAP) sensor responds to changes in intake manifold pressure which gives an indication of the engine load. The MAP sensor has a 5-volt reference circuit, and a signal circuit. The Powertrain Control Module (PCM) supplies 5 volts to the MAP sensor on the 5-volt reference circuit, and provides a ground on the low reference circuit. The MAP sensor provides a signal to the PCM on the signal circuit which is relative to the pressure changes in the manifold. With low manifold absolute pressure such as during idle or deceleration, the PCM should detect a low MAP sensor signal voltage. With high manifold absolute pressure such as ignition ON, with the engine OFF or Wide Open Throttle (WOT), the PCM should detect a high MAP sensor signal voltage. Certain vehicle models will also use the MAP sensor in order to calculate the Barometric Pressure (BARO) when the ignition is turned ON, with the engine OFF. The BARO reading may also be updated whenever the engine is operated at WOT. The PCM monitors the MAP sensor signal for voltage outside of the normal range. If the PCM detects a MAP signal voltage that is intermittently low, DTC P1107 will set.

DTCs P0121, P0122 or P0123 are not set.
The ignition is ON.
The throttle angle is more than 0 percent when the engine speed is less than 1000 RPM Or
The throttle angle is more than 10 percent when the engine speed is more than 1000 RPM.

The MAP sensor voltage is intermittently less than 0.1 volt.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

4 Many intermittent open or shorted circuits come and go with harness/connector movement caused by vibration, by engine torque, and by bumps. This step attempts to recreate this condition.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start the engine. Monitor the DTC Information with a scan tool. Does the scan tool indicate that DTC P1635 or P0107 is current? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Observe the MAP sensor voltage with a scan tool. Does the scan tool indicate that the voltage is less than 0.1 volt? If yes, go to step 5 . If no, go to next step.
Turn ignition off. Turn ignition on, with engine off. Observe the MAP sensor voltage with a scan tool, while moving the MAP sensor connector, wiring harness related to MAP sensor and PCM connector. Does the scan tool indicate that the MAP sensor voltage is less than 0.1 volt? If yes, go to next step. If no, go to step 11 .
Turn ignition off. Disconnect the MAP sensor electrical connector. Turn ignition on, with engine off. Measure the voltage from the 5-volt reference circuit of the MAP sensor to a known-good ground. Does the voltage measure about 5 volts? If yes, go to next step. If no, go to step 7 .
Connect a 3-amp fused jumper wire between the 5-volt reference circuit of the MAP sensor and the signal circuit of the MAP sensor. Does the scan tool indicate that the voltage is about 5 volts? If yes, go to step 9 . If no, go to step 8 .
Test the 5-volt reference circuit of the MAP sensor for an open. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Test the signal circuit of the MAP sensor for a short to ground or for an open. Did you find and correct the condition? If yes, go to step 11 . If no, go to step 10 .
Inspect for poor connections at the MAP sensor. Did you find and correct the condition? If yes, go to step 11 . If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Inspect for poor connections at the PCM. Did you find and correct the condition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1111: IAT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Intake Air Temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT signal circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an intermittent high IAT signal voltage, indicating a low temperature, DTC P1111 sets.

DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0502 or P0503 are not set.
The VSS is less than 35 MPH.
The MAF is less than 12 g/s.
The ECT is more than 140°F (60°C).
The engine run time is more than 180 seconds.

The Intake Air Temperature (IAT) is less than -38°F (-39°C) for more than 3 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the DTC Information with a scan tool. Is DTC P0113 set? If yes, go to «DTC P0113: IAT SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0113-iat-sensor-circuit) . If no, go to next step.
Turn ignition off. Disconnect the IAT sensor. Inspect for poor connection at the harness connector of the IAT sensor. Repair connector as necessary. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Test the IAT signal circuit between the IAT sensor and the PCM for and intermittent open. Repair as necessary. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Test the IAT signal circuit between the IAT sensor and the PCM for an intermittent short to a separate voltage source. Repair as necessary. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Test the low reference circuit for and intermittent open. Repair as necessary. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Disconnect the PCM connector at the PCM. Inspect for poor connections at the harness connector of the PCM. Repair connector as necessary. Did you find and correct the condition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Use the scan tool to clear the DTCs. Turn off the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1112: IAT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Intake Air Temperature (IAT) sensor is a variable resistor, sometimes called a thermistor. The IAT sensor has a signal circuit and a low reference circuit. The IAT sensor measures the temperature of the air entering the engine. The Powertrain Control Module (PCM) supplies 5 volts to the IAT signal circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the IAT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the IAT signal circuit. If the PCM detects an intermittent low IAT signal voltage, indicating a high temperature, DTC P1112 sets.

DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0502, or P0503 are not set.
The engine run time is more than 10 seconds.
The Vehicle Speed Sensor (VSS) indicates that vehicle speed is more than 25 MPH.

The Intake Air Temperature (IAT) is more than 253°F (123°C) for 20 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the DTC Information with a scan tool. Is DTC P0112 set? If yes, go to «DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0112-iat-sensor-circuit) . If no, go to next step.
Test the IAT signal circuit between the IAT sensor and the PCM for an intermittent short to ground. Repair as necessary. Did you find and correct the condition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Use the scan tool to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1114: ECT SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The engine run time is more than 5 seconds.

The PCM detects an intermittent high ECT sensor temperature when the engine is running and when the run time exceeds 5 seconds.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 If there is no driveability complaint associated with DTC and if the DTC does not reset, then the system is okay.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ON the ignition. Start the engine. Does the scan tool indicate that DTC P0117 also failed? If yes, go to «DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0117-ect-sensor-circuit) . If no, go to next step.
Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature while moving the sensor connector and the PCM connector. Does the scan tool indicate an abrupt change in value? If yes, go to step 6 . If no, go to next step.
Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature while moving the wiring harness at the sensor and the PCM. Does the scan tool indicate an abrupt change in value? If yes, go to step 7 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close as possible to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC reset? If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, system okay.
Repair the connector or terminal as necessary. After repairs, go to step 8 .
Repair the harness or wiring as necessary. After repairs, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

An ECT sensor or PCM which is intermittently shorted, open, or skewed is possible yet very unlikely.
An intermittent short to ground in the ECT sensor signal circuit could result in a DTC P1114. If the low ECT voltage (high temperature) reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) .
Use the sensor Temperature-vs-Resistance table in order to test the coolant sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability complaints. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.
If an intermittent condition is suspected, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P1115: ECT SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Engine Coolant Temperature (ECT) sensor is a variable resistor, sometimes called a thermistor, that measures the temperature of the engine coolant. The Powertrain Control Module (PCM) supplies 5 volts to the ECT signal circuit. When the ECT is cold, the sensor resistance is high. When the ECT increases, the sensor resistance lowers. With high sensor resistance, the PCM detects a high voltage on the ECT signal circuit. With lower sensor resistance, the PCM detects a lower voltage on the ECT signal circuit. If the PCM detects an excessively high signal voltage, which is a low temperature indication, DTC P1115 sets.

The engine run time is more than 5 seconds.

The PCM detects an intermittent low ECT sensor temperature while the engine is running and run time exceeds 5 seconds.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

5 If there is no driveability complaint associated with DTC and the DTC does not reset, then the system is okay.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ON the ignition. Start the engine. Does the scan tool indicate that DTC P0118 also failed? If yes, go to «DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0118-ect-sensor-circuit) . If no, go to next step.
Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature while moving the sensor connector and the PCM connector. Does the scan tool indicate an abrupt change in value? If yes, go to step 6 . If no, go to next step.
Turn ignition on, with engine off. With a scan tool, observe the ECT sensor temperature while moving the wiring harness at the sensor and the PCM. Does the scan tool indicate an abrupt change in value? If yes, go to step 7 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC reset? If yes, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If no, system is okay.
Repair the connector/terminal as necessary. After repairs, go to step 8 .
Repair the harness wiring as necessary. After repairs, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Check for any of the following conditions

An intermittent open or short to voltage in the ECT sensor signal circuit could result in a DTC P1115. If the high ECT voltage (low temperature) reading is present, additional sensor circuit voltage codes could be set. Refer to any non-intermittent DTCs that are set. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) .
Use the Temperature-vs-Resistance value table in order to test the coolant sensor at various temperature levels in order to evaluate the possibility of a skewed sensor. A skewed sensor could result in poor driveability complaints. Refer to appropriate SENSOR RESISTANCE table in appropriate SENSOR OPERATING RANGE CHARTS article.
If an intermittent condition is suspected, refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P1121: TP SENSOR CIRCUIT INTERMITTENT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with a 5-volt reference circuit, low reference circuit and a signal circuit.

Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to greater than 4 volts through the TP sensor signal circuit. If the PCM detects an intermittent excessively high signal voltage, this DTC will set.

The ignition is ON.

The TP sensor intermittently indicates a throttle position signal more than 4.9 volt for 0.5 second.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

7 This test determines an intermittent faulty TP sensor utilizing the Digital Multimeter's (DMM) MIN MAX, 100-millisecond capture mode.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Test all 5-volt reference circuits for an intermittent short to voltage. Turn ignition off. Disconnect the TP sensor. Connect a Digital Multimeter (DMM) between the TP sensor 5-volt reference circuit at the TP sensor harness connector and ground. Turn ignition on, with engine off. Lightly touch and move the related engine wiring harnesses and connectors for all 5-volt reference circuits while observing voltage. Any change in voltage indicates the area where a short to voltage may be found. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Test the TP sensor signal circuit for an intermittent short to voltage. Turn ignition off. Connect a DMM between the TP sensor signal circuit at the TP sensor harness connector and ground. Turn ignition on, with engine off. Lightly touch and move the related engine wiring harnesses and connectors while observing voltage. Any change in voltage indicates the area where a short to voltage may be found. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Test the TP sensor low reference circuit for an intermittent open or high resistance. Turn ignition off for 30 seconds. Connect a DMM between the TP sensor low reference circuit at the TP sensor harness connector and ground. Lightly touch and move the related engine wiring harnesses and connectors while observing resistance. Any change in resistance indicates the area where an open or high resistance may be found. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Inspect for poor connections at the TP sensor harness connector. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Inspect for poor connections at the PCM harness connector. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Connect two jumper wires at the TP sensor, one at the signal terminal, and one at the 5-volt reference terminal. With a DMM set to the 40 k/ohms scale, connect the DMM to the jumper wires. Ensure a good connection at the TP sensor and DMM test leads. Press the MIN MAX button on the DMM. Slowly depress the accelerator pedal to Wide Open Throttle (WOT) and back to the closed throttle position several times. Press the MIN MAX button and record the MAX reading. Press the MIN MAX button again and record the MIN reading. Remove the jumper wire at the 5-volt reference terminal and connect the jumper wire to the low reference terminal and repeat steps 2 - 7 . Did you record a MAX value of OL or record a MIN value of 0 ohms in either test? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Replace the TP sensor. After repairs, go to next step.
Use a scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1122: TP SENSOR CIRCUIT INTERMITTENT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with a 5-volt reference, low reference and a signal circuit.

The ignition is ON.

TP sensor intermittently indicates a throttle position signal less than 0.95 volt for 0.5 second.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

6 This test determines an intermittent faulty TP sensor utilizing the DMM's MIN MAX, 100 millisecond capture mode.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Test the 5-volt reference circuit of the TP sensor for an intermittent open, for a high resistance, and a short to ground. Turn ignition off. Disconnect the TP sensor. Connect a Digital Multimeter (DMM) between the TP sensor 5-volt reference circuit at the TP sensor harness connector and ground. Turn ON the ignition. Lightly touch and move the related engine wiring harnesses and connectors for all 5 volt reference circuits while observing voltage. Any change in voltage indicates the area where a 5-volt reference circuit fault may be found. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Test the signal circuit of the TP sensor for an intermittent open, a high resistance, and a short to ground. Reconnect the TP sensor. Install a scan tool and observe the TP voltage parameter. Lightly touch and move the related engine wiring harnesses and connectors for the TP signal circuit while observing voltage. Any change in voltage indicates the area where a TP signal circuit fault may be found. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Inspect for poor connections at the TP sensor harness connector. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 8 . If no, go to next step.
Connect two jumper wires at the TP sensor, one at the signal terminal, one at the 5-volt reference terminal. With a DMM set to 40 k/ohms scale, connect the DMM to the jumper wires. Ensure a good connection at the TP sensor and DMM test leads. Press the MIN MAX button on the DMM. Slowly depress the accelerator pedal to Wide Open Throttle (WOT) and back to the closed throttle position several times. Press the MIN MAX button and record the MAX reading. Press the MIN MAX button again and record the MIN reading. Remove the jumper wire at the 5-volt reference terminal and connect the jumper wire to the low reference terminal and repeat steps 2 - 6 . Did you record a MAX value of OL or record a MIN value of 0 ohms in either test? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Replace the TP sensor. After repairs, go to next step.
Use a scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1133: HO2S INSUFFICIENT SWITCHING (BANK 1; SENSOR 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. This DTC will set if the HO2S 1 voltage did not switch enough times during a calibrated time period.

Each HO2S 1 has the following circuits: HO2S 1 high signal, HO2S 1 low reference, HO2S 1 heater ignition voltage, HO2S 1 heater low control and low reference loop.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The engine run time is longer than 3.3 minutes.
The system voltage is 9-18 volts.
The system is in closed loop.
The engine coolant is more than 167°F (70°C).
The TP sensor angle is more than 2 percent.
The MAF is 13-29 g/s.
The engine speed is 1300-3000 RPM.

The DTC will set if either of the following conditions are present for a 100 second monitoring period

PCM has monitored fewer than 25 rich-to-lean switches.
PCM has monitored fewer than 25 lean-to-rich switches.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

PCM turns OFF the MIL after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.
6 This step checks the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.
8 This step checks for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.
9 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage fluctuate rapidly greater than and less than the specified value of 350-550 mV? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a Digital Multimeter (DMM). Is the HO2S voltage within 0.425-0.500 volt? If yes, go to next step. If no, go to step 6 .
Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 1 harness connector high signal circuit, and low reference circuit. Turn ignition on, with engine off. Observe the HO2S 1 voltage on the scan tool. Does the scan tool display less than 25 mV? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Disconnect both PCM connectors. Measure the resistance of each of the following circuits with a DMM: HO2S 1 high signal circuit between HO2S connector and PCM connector, HO2S 1 low reference circuit between HO2S connector, and PCM connector low reference loop between PCM harness connector terminals C1-29 and C2- 80. Is resistance of each circuit less than 5 ohms? If yes, go to step 11 . If no, go to next step.
Repair the circuit that measured a high resistance or an open. After repairs, go to step 14 .
Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S heater ignition voltage circuit, and HO2S heater low control circuit terminals, on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to «DTC P0135: HO2S HEATER PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0135-ho2s-heater-performance) .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the HO2S 1. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1134: HO2S TRANSITION TIME RATIO (BANK 1; SENSOR 1)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content of the exhaust stream. When the vehicle is first started the Powertrain Control Module (PCM) operates in an Open Loop mode, ignoring the HO2S signal voltage when calculating the air/fuel ratio. The PCM supplies the HO2S with a reference, or bias, voltage of about 450 mV. The HO2S generates a voltage within a range of 0-1000 mV that fluctuates greater than and less than bias voltage once in Closed Loop. A high HO2S voltage output indicates a rich fuel mixture. A low HO2S voltage output indicates a lean mixture. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature, and to provide an accurate voltage signal. The PCM calculates a transition time ratio rich-to-lean and lean-to-rich HO2S voltage transitions. If the calculated transition time ratio is incorrect this DTC will set.

Each HO2S 1 has the following circuits: HO2S 1 high signal, HO2S 1 low reference, HO2S 1 heater ignition voltage, HO2S 1 heater low control, and low reference loop circuit.

DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0201, P0202, P0203, P0204, P0205, P0206, P0410, P0440, P0442, P0443, P0446, P0449, or P1441 are not set.
The system is in Closed Loop.
The engine has been running for at least 60 seconds.
The MAF is 13-29 g/s.
The engine speed is 1300-3000 RPM.
The throttle angle is 3-35 percent.
The system voltage is 9-18 volts.
The ECT is more than 122°F (50°C).

The average transition time ratio is not within 0.4-4.2 during a 100 second monitoring period.

The PCM illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.

The PCM turns OFF the MIL light after 3 consecutive ignition cycles that the diagnostic runs and passes.
A current, DTC last test fails, clears when the diagnostic runs and passes.
A DTC stored in history clears after 40 warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
A scan tool can be used to clear the DTC.

The numbers below refer to the step numbers in the diagnostic procedures.

2 The HO2S 1 voltage may default to the bias voltage. The DTC should be cleared and the Freeze Frame/Failure Records data recorded before proceeding. A normally functioning HO2S 1 voltage signal will fluctuate greater than and less than the bias voltage amount.
4 A voltage reading other than the specified amount in this step indicates an open circuit condition in the high signal circuit or the PCM.
6 This step checks the HO2S 1 signal circuits from the HO2S connector and the PCM connectors, including the low reference loop between the PCM connectors.
8 This step checks for correct HO2S 1 heater circuit operation up to the HO2S connector. The heater low control is controlled by the PCM. The engine must be running to enable the HO2S heater.
9 The conditions listed in the table may contribute to the failure of the HO2S. The conditions listed apply only to this type of failure.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Allow the engine to idle at operating temperature. Observe the HO2S 1 voltage parameter with a scan tool. Clear the DTC and record the Freeze/Frame Failure Records data if the HO2S 1 voltage is fixed at bias voltage. Does the HO2S 1 voltage fluctuate rapidly greater than and less than the specified value of 350-550 mV? If yes, go to next step. If no, go to step 4 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the HO2S 1 connector. Turn ignition on, with engine off. Measure the voltage from the high signal circuit of the HO2S 1 harness connector, on the engine side, to a good ground with a Digital Multimeter (DMM). Is the HO2S voltage within 0.425-0.500 volt? If yes, go to next step. If no, go to step 6 .
Turn ignition off. Connect a 3-amp fused jumper wire between the HO2S 1 high signal circuit, and the HO2S 1 low reference circuit. Turn ignition on, with engine off. Observe the HO2S 1 voltage on the scan tool. Does the scan tool display less than 25 mV? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Disconnect both PCM connectors. Measure the resistance of each of the following circuits with a DMM: HO2S 1 high signal circuit between HO2S connector and PCM connector, HO2S 1 low reference circuit between HO2S connector and PCM connector low reference loop between PCM harness connector terminals C1-29 and C2-80. Is resistance of each circuit less than 5 ohms? If yes, go to step 11 . If no, go to next step.
Repair the circuit that measured a high resistance or an open. After repairs, go to step 14 .
Remove the jumpers from the HO2S 1 terminals. Connect a test light between the HO2S heater ignition voltage circuit, and HO2S heater low control circuit terminals on the engine harness side. Start the engine. Does the test light illuminate? If yes, go to next step. If no, go to «DTC P0135: HO2S HEATER PERFORMANCE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0135-ho2s-heater-performance) .
Inspect for the following conditions that may affect the HO2S operation: HO2S for contamination, chafed, burnt, cut, pinched, or otherwise damaged HO2S wiring, exhaust system leaks or restrictions, EVAP canister purge, and for proper fuel pressure. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
Inspect for poor connections at the HO2S 1 connector. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
Inspect for poor connections at the PCM harness connectors. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
Replace the HO2S 1. After repairs, go to step 14 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1336: CRANKSHAFT POSITION SYSTEM VARIATION NOT LEARNED

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Crankshaft Position (CKP) system variation learn feature is used to calculate reference period errors caused by slight tolerance variations in the crankshaft, and the CKP sensors. The calculated error allows the Powertrain Control Module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load.

The PCM stores the CKP system variation values after a learn procedure has been performed. This DTC set indicates that the CKP system variation values have not been stored in the PCM and the CKP system variation learn procedure must be performed.

DTCs P0336, P0341 or P1374 are not set.
The ECT is more than 158°F (70°C).

The CKP system variation values are not stored in the PCM memory.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Perform the CKP system variation learn procedure. Refer to CKP SYSTEM VARIATION LEARN PROCEDURE under «PROGRAMMING»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__programming) . Is action complete? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Clear DTCs with scan tool. Turn ignition off. Start engine. Operate vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The CKP system variation compensating values are stored in PCM memory after a learn procedure has been performed. If the actual CKP variation is not within the CKP system variation compensating values stored in the PCM, DTC P0300 may set.

The CKP system variation learn procedure is also required when the following service procedures have been performed, regardless of whether DTC P1336 is set.

Engine replacement.
PCM replacement.
A harmonic balancer replacement.
Crankshaft replacement.
CKP sensor replacement.
Any engine repairs which disturb the crankshaft to CKP sensor relationship.

If the CKP system variation learn procedure cannot be performed successfully, inspect for the following conditions and correct as necessary

A damaged reluctor wheel.
Excessive crankshaft runout.
A damaged crankshaft.
Interference in the signal circuit of the CKP sensor.
A coolant temperature that is not within the Condition For Running the DTC.
The ignition switch is in the ON position until the battery is drained.
A PCM power disconnect with the ignition ON may erase the stored value and set the DTC P1336.
A PCM power disconnect with the ignition ON may erase the stored value and set the DTC P1336.

DTC P1351: IC CIRCUIT HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Ignition Control (IC) module has independent power and ground circuits. The circuits between the IC module and the Powertrain Control Module (PCM) consist of the following circuits

The IC timing signal.
The IC timing control.
The low-resolution engine speed signal.
A low reference signal.

The IC module sends 3x signals to the Powertrain Control Module (PCM). The IC module controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions

The PCM receives the second 3x signal.
The PCM applies 5 volts to the IC timing signal circuit.
The timing advance switches to PCM control.

The engine speed is greater than 600 RPM.

The PCM detects an open in the IC timing signal circuit.
The condition is present for 300 3X reference periods, 100 crankshaft revolutions.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Disconnect the PCM. Connect Digital Multimeter (DMM) between the IC and low reference circuits. Turn ON the ignition. Observe the resistance value on the Digital Multimeter (DMM). Does the resistance measure less than 500 ohms? If yes, go to step 5 . If no, go to next step.
Turn ignition off. Leave the PCM disconnected. Disconnect the IC module connector. Test for an open in the IC control circuit. Did you find and correct the condition? If yes, go to step 9 . If no, go to step 6 .
Test for poor terminal connections at the PCM. Did you find and correct the condition? If yes, go to step 9 . If no, go to step 8 .
Test for poor terminal connections at the IC module. Did you find and correct the condition? If yes, go to step 9 . If no, go to next step.
Replace the IC module. After repairs, go to step 9 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn OFF ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The engine will start and may run with IC module controlling spark timing. If condition is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1352: IC OUTPUT HIGH/PULSE DETECTED

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Ignition Control (IC) module has independent power and ground circuits. The circuits between the IC module and the Powertrain Control Module (PCM) consist of the following circuits

The IC timing signal.
The IC timing control.
The low resolution engine speed signal.
A low reference signal.

The Ignition Control (IC) module sends 3x signals to the Powertrain Control Module (PCM). The IC module controls the timing advance during engine cranking. The timing advance changes to PCM control after the following actions

The PCM receives the second 3x signal.
The PCM applies 5 volts to the IC timing signal circuit.
The timing advance switches to PCM control.

The engine is running.

The PCM detects an open circuit in the IC signal circuit.
The condition is present for 300 3X reference periods, 106 crankshaft revolutions.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the Freeze Frame/Failure Records data for the DTC. Turn OFF ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the PCM. Turn ON the ignition. Probe the low reference circuit with a test light connected to battery positive voltage. Does the test light illuminate? If yes, go to step 6 . If no, go to next step.
Inspect the low reference circuit for an open. Did you find and correct the condition? If yes, go to step 6 . If no, go to next step.
Inspect for poor connections at the IC module. Did you find and correct the condition? If yes, go to next step. If no, go to step 7 .
Turn ignition off. Disconnect the PCM. Connect DMM between the IC control and low reference circuits. Turn ON the ignition. Probe the IC timing signal circuit with a test light connected to battery positive voltage. Does the resistance measure greater than 5000 ohms? If yes, go to step 8 . If no, go to next step.
Turn ignition off. Leave the PCM disconnected. Disconnect the IC module connector. Test for an open in the IC timing signal circuit. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Inspect for poor terminal connections at the PCM. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Inspect for poor terminal connections at the IC module. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Replace the IC module. After repairs, go to step 12 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The engine will start and may run in bypass mode timing. If condition is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1361: IC CIRCUIT LOW VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Ignition Control (IC) module has independent power and ground circuits. The circuits between the IC module and the Powertrain Control Module (PCM) consist of the following circuits

The IC timing signal.
The IC timing control.
The low-resolution engine speed signal.
A low reference signal.

The PCM receives the second 3x signal.
The PCM applies 5 volts to the IC timing signal circuit.
The timing advance switches to PCM control.

The engine speed is more than 600 RPM.
DTC P1351 did not set.

The PCM does not monitor IC pulses while IC mode spark advance is commanded.
The condition is present for 300 3X reference periods, 100 crankshaft revolutions.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step determines if DTC P1362 is also set.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. With a scan tool, monitor the DTC information for DTC P1362 in the PCM. Does the scan tool indicate that DTC P1362 is current? If yes, go to step 6 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the PCM. Turn ON the ignition. Probe the IC timing control circuit with a test light connected to ground. Does the test light illuminate? If yes, go to next step. If no, go to step 14 .
Turn ignition off. Leave the PCM disconnected. Disconnect the IC module connector. Turn ON the ignition. Probe the IC timing control circuit with a test light connected to ground. Does the test light illuminate? If yes, go to step 10 . If no, go to step 13 .
Turn ignition off. Disconnect the IC module. Probe the IC timing control circuit at the PCM with a test light connected to battery positive voltage. Does the test light illuminate? If yes, go to step 11 . If no, go to next step.
Leave the ignition OFF. Leave the IC module disconnected. Probe the IC timing signal circuit with a test light connected to battery positive voltage. Does the test light illuminate? If yes, go to step 12 . If no, go to next step.
Leave the ignition OFF. Leave the PCM disconnected. Leave the IC module disconnected. Test for a short between the IC timing control and IC timing signal circuits. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
Leave the ignition OFF. Reconnect the IC module. Leave the PCM disconnected. Turn ON the ignition. Using the DMM, observe the resistance between the IC timing control circuit and a known-good ground while probing the IC timing signal circuit with a test light connected to battery positive voltage. Does the resistance toggle between the ranges of 100-600 ohms to 6000-10,000 ohms? If yes, go to step 14 . If no, go to step 13 .
Repair the short to voltage in the IC timing control circuit. After repairs, go to step 15 .
Repair the short to ground or the low reference in the IC timing control circuit. After repairs, go to step 15 .
Repair the short to ground or the low reference in the IC timing signal circuit. After repairs, go to step 15 .
Replace the IC module. After repairs, go to step 15 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 3 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1362: IC CYLINDER NO. 2 NOT TOGGLING AFTER ENABLE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Ignition Control (IC) module has independent power and ground circuits. The circuits between the IC module and the Powertrain Control Module (PCM) consist of the following circuits

The IC timing signal.
The IC timing control.
The low resolution engine speed signal.
A low reference signal.

The PCM receives the second 3x signal.
The PCM applies 5 volts to the IC timing signal circuit.
The timing advance switches to PCM control.

The engine is running.

The PCM detects a short to voltage in the IC timing signal circuit.
The condition is present for 300 3X reference periods, 100 crankshaft revolutions.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step determines if DTC P1361 is also set.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Turn ignition on, with engine off. Monitor the DTC information for DTC P1361 in the Powertrain Control Module (PCM) with a scan tool. Does the scan tool indicate that DTC P1361 is current? If yes, go to step 6 . If no, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off. Disconnect the PCM. Turn ON the ignition. Probe the Ignition Control (IC) timing signal circuit with a test light connected to ground. Does the test light illuminate? If yes, go to next step. If no, go to step 14 .
Turn ignition off. Leave the PCM disconnected. Disconnect the IC module connector. Turn ON the ignition. Probe the IC timing signal circuit with a test light connected to ground. Does the test light illuminate? If yes, go to step 10 . If no, go to step 13 .
Turn ignition off. Disconnect the PCM. Disconnect the IC module. Probe the IC timing control circuit with a test light connected to battery positive voltage. Does the test light illuminate? If yes, go to step 11 . If no, go to next step.
Leave the ignition OFF. Leave the PCM disconnected. Leave the IC module disconnected. Probe the IC timing signal circuit with a test light connected to ground. Does the test light illuminate? If yes, go to step 12 . If no, go to next step.
Leave the ignition OFF. Leave the PCM disconnected. Leave the IC module disconnected. Test for a short between the IC timing control and IC timing signal circuits. Did you find and correct the condition? If yes, go to step 15 . If no, go to next step.
Leave the ignition OFF. Reconnect the IC module. Leave the PCM disconnected. Turn ON ignition. Using DMM, observe the resistance between the IC timing control circuit and a known-good ground while probing the IC timing signal circuit with a test light connected to battery positive voltage. Does the resistance toggle between the two indicated ranges of 100-600 ohms to 6000-10,000 ohms? If yes, go to step 14 . If no, go to step 13 .
Repair short to voltage in the IC timing signal circuit. After repairs, go to step 15 .
Repair short to ground in the IC timing control circuit After repairs, go to step 15 .
Repair short to ground in the IC timing signal circuit. After repairs, go to step 15 .
Replace IC module. After repairs, go to step 15 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 3 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1374: 3X REFERENCE CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The 3X reference signal is produced by the Ignition Control (IC) module. The IC module calculates the 3X reference signal by dividing the Crankshaft Position (CKP) sensor 7X pulses by 2 when the engine is running and the CKP synchronizing pulses are being received. The Powertrain Control Module (PCM) uses the 3X reference signal to calculate the engine RPM and the CKP at engine speeds greater than 1600+/-150 RPM. The PCM also uses these pulses to initiate injector pulses. The PCM compares the 3X reference pulses to the 24X CKP pulses and the Camshaft Position (CMP) pulses. If the PCM receives an incorrect number of pulses on the 3X circuit a DTC P1374 will set and the PCM will use the 24X CKP reference circuit for fuel and ignition control. The engine will continue to start and run using only the 24X CKP and CMP sensor signals.

The engine is running, and the 24X reference pulses are being received.

The ratio of 24X reference pulses to 3X reference pulses received by the PCM does not equal 8.
The ratio of 24X reference pulses to CMP PCM input pulses received by the PCM equals 48.
The conditions are present for more than 10 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Attempt to start the engine. Does the engine start and run? If yes, go to step 4 . If no, go to next step.
Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or within the parameters observed in the Freeze Frame/Failure Records. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the 6-way ignition control module connector. Remove the injector fuse. Turn ignition on, with engine off. Momentarily probe the 3X reference signal circuit at the ignition module harness connector with a test light connected to B+. Observe the Engine Speed parameter with a scan tool. Is an Engine Speed displayed? If yes, go to step 8 . If no, go to next step.
Did the test light illuminate? If yes, go to step 7 . If no, go to next step.
Turn ignition off. Disconnect the PCM. Turn ignition on, with engine off. Test the 3X reference circuit of the ignition control module for an open or a short to voltage. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Turn ignition off. Disconnect the PCM. Test the 3X reference circuit of the ignition control module for a short to ground. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 9 .
Test for an intermittent and for a poor connection at the ignition control module. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 10 .
Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step 12 . If no, go to step 11 .
Replace ignition control module. After repairs, go to step 12 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1374 can be caused by secondary components leaking high voltage into the IC module.

Check for any of the following conditions

Incorrect harness routing near secondary ignition components.
Ignition coil arcing to wiring harness or IC module Inspect the ignition coils for cracks, carbon tracking and other signs of damage.
Secondary ignition wires arcing to the wiring harness.
If the DTC is determined to be intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

DTC P1380: EBTCM DTC DETECTED ROUGH ROAD DATA UNUSABLE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) receives rough road information from the Electronic Brake Control Mode/Electronic Brake Traction Control Module (EBCM/EBTCM) on the serial data circuit. The PCM uses the rough road information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. The EBCM/EBTCM transmits rough road information based on inputs from the wheel speed sensors. If the EBCM/EBTCM detects a condition which will not allow the EBCM/EBTCM to properly identify rough road situations while a misfire condition is being detected by the PCM, DTC P1380 will be set.

The engine load is less than 8 percent.
The engine speed is less than 5000 RPM.
The vehicle speed is greater than 10 MPH.
A misfire DTC is occurring and is requesting the MIL to be illuminated.

The PCM has detected a EBCM/EBTCM rough road sensing error.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

Did you perform diagnostic system check - engine controls. If yes, perform diagnostic system check - ABS in appropriate ANTI-LOCK article in BRAKES. If no, go to «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM.

DTC P1380 set indicates that the Anti-Lock Brake System (ABS) system has detected a malfunction which will not allow the EBCM/EBTCM to transmit correct rough road data to the PCM. Refer to Diagnostic System Check - ABS in appropriate ANTI-LOCK article in BRAKES.

DTC P1381: MISFIRE DETECTED NO EBTCM/PCM SERIAL DATA

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) uses the rough road information to enhance the misfire diagnostic by distinguishing crankshaft speed variations caused by driving on rough road surfaces from variations caused by true misfires. The Electronic Brake Control Mode/Electronic Brake Traction Control Module (EBCM/EBTCM) transmits rough road information based on inputs from the wheel speed sensors. If a loss of communication occurs which causes the PCM not to receive rough road information while DTC P0300 is requesting the Malfunction Indicator Light (MIL), DTC P1381 will set.

The engine load is less than 87 percent.
The engine speed is less than 5000 RPM.
The vehicle speed is greater than 10 MPH.
A misfire DTC is occurring and is requesting the MIL to be illuminated.

The PCM is detecting a loss of communication with the EBCM/EBTCM for at least 5 seconds.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step ensures that the EBCM/EBTCM is capable of transmitting the serial data on the class 2 serial data circuit.
4 This step tests the class 2 serial data circuit at the EBCM/EBTCM for correct voltage.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Turn ON the ignition switch. Select chassis application on the scan tool. Attempt to display Anti-Lock Brake System (ABS) data on the scan tool. Can ABS data be displayed? If yes, go to next step. If no, go to step 4 .
Test the serial data circuit for an open or a poor connection between the PCM and the EBCM. Did you find and correct the condition? If yes, system okay. If no, problem is intermittent. Refer to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Turn ignition off switch. Disconnect the EBCM. Turn ON the ignition switch. Using a Digital Multimeter (DMM) measure voltage on the serial data circuit at the EBCM harness connector. Does voltage vary between 1-5 volts? If yes, go to next step. If no, go to step 6 .
Inspect for a poor connection at the EBCM. Did you find and correct the condition? If yes, go to step 7 . If no, go to next step.
Test for an open in the serial data circuit to the EBCM. Did you find and correct the condition? If yes, go to next step. If no, diagnose anti-lock brake systems. See appropriate ANTI-LOCK article in BRAKES.
Turn ON the ignition switch. Select chassis application on the scan tool. Attempt to display ABS data on the scan tool. Can ABS data be displayed? If yes, system is okay. If no, go to step 4 .

DTC P1404: EGR SYSTEM (VALVE NO. 2)

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) monitors the Exhaust Gas Recirculation (EGR) valve pintle position input in order to ensure that the valve responds properly to the commands from the PCM. When the ignition switch is turned ON, the PCM learns the EGR learned minimum position. The PCM compares the EGR learned minimum position to the EGR position sensor when the EGR valve is commanded closed. If the EGR position sensor indicates that the EGR valve is still open when the PCM is commanding the EGR valve closed, this DTC will set.

The system voltage is greater than 11 volts.

The EGR position sensor is 0.2 volt more than the EGR learned minimum position when the desired EGR position is commanded to 0 percent.
The above condition is present twice.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

2 This step verifies that the malfunction is present.
4 If DTC P1404 will only set during certain conditions, the malfunction may be intermittent. Refer to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . If an intermittent wiring problem is not present, test for a faulty connection at the PCM or the EGR valve. If the connections are okay, and if DTC P1404 continues to set, replace the EGR valve.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Install a scan tool. Start the engine. With a scan tool, observe the EGR position sensor parameter. Does the scan tool indicate that the EGR position sensor is 0 percent? If yes, go to next step. If no, go to step 5 .
Turn ignition on, with engine off. With a scan tool, command the EGR valve from 0 to 100 percent. Does the desired EGR position remain within 15 percent of the EGR position sensor at all commanded positions? If yes, go to next step. If no, go to step 6 .
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Turn ignition off. Disconnect the EGR valve. Turn ignition on, with engine off. With a scan tool, observe the EGR position sensor parameter. Does the scan tool indicate that the EGR position sensor is at 0 percent? If yes, go to next step. If no, go to step 9 .
Measure the voltage from the 5-volt reference circuit of the EGR position sensor to the low reference circuit of the EGR position sensor. Does the DMM display voltage about 5 volts? If yes, go to next step. If no, go to step 8 .
Connect a fused jumper between the 5-volt reference circuit of the EGR position sensor and the EGR valve position signal circuit of the EGR position sensor. Does the scan tool indicate that the EGR position sensor is about 100 percent? If yes, go to step 13 . If no, go to step 11 .
Measure the voltage from the 5-volt reference circuit of the EGR position sensor to a good ground. Does the DMM display voltage about 5 volts? If yes, go to step 10 . If no, go to step 12 .
Test the EGR valve position signal circuit for a short to voltage. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
Test the EGR position sensor low reference circuit for an open or for high resistance. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
Test the signal circuit for high resistance or for a high resistance short to ground. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
Test the 5-volt reference circuit of the EGR position sensor for an open, for a short to ground, or for a short to voltage. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 14 .
Inspect for poor connections at the harness connector of the EGR valve. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 15 .
Inspect for poor connections at the harness connector of the PCM. Did you find and correct the condition? If yes, go to step 17 . If no, go to step 16 .
Replace the EGR valve. After repairs, go to step 17 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

Inspect for excessive deposits on the EGR valve pintle or seat. Remove EGR valve. Inspect for deposits that may interfere with the EGR valve pintle extending completely or may cause the pintle to stick. If problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1441: EVAP SYSTEM FLOW DURING NON-PURGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

This DTC tests for undesired intake manifold vacuum flow to the Evaporative Emission (EVAP) system. The control module seals the EVAP system by commanding the EVAP canister purge valve OFF and the EVAP canister vent valve ON. The control module monitors the Fuel Tank Pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If vacuum in the EVAP system is more than a predetermined value within a predetermined time, this DTC sets.

The following table illustrates the relationship between the ON and OFF states, and the Open or Closed states of the EVAP canister purge and vent valves. See EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP table.

Control Module Command	EVAP Canister Purge Valve	EVAP Canister Vent Valve
ON	Open	Closed
OFF	Closed	Open

EVAP CANISTER PURGE & VENT VALVE RELATIONSHIP

DTCs P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0440, P0442, P0443, P0446, P0449, P0452, P0453, P1106, P1107, P1112, P1114, P1115, P1121, or P1122 are not set.
The ignition voltage is 10-18 volts.
The BARO is more than 75 kPa.
The fuel level is 15-85 percent.
The ECT is 39-86°F (4-30°C).
The IAT is 39-86°F (4-30°C).
The start-up ECT and IAT are within 16°F (9°C).
The VSS is less than 75 MPH.

The control module detects vacuum during a non purge condition.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The number below refers to the step number on the diagnostic procedure.

4 This test determines if the EVAP canister purge valve can seal.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Are DTCs P0443, P0449, P0452 or P0453 also set? If yes, go to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, go to next step.
Remove the fuel fill cap. Turn ignition on, with engine off. Monitor the Fuel Tank Pressure (FTP) sensor with a scan tool. Does the scan tool indicate fuel tank pressure within -0.5 to 0.5 in. H2O? If yes, go to next step. If no, go to «DTC P0453: FUEL TANK PRESSURE SENSOR CIRCUIT - HIGH VOLTAGE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__dtc-p0453-fuel-tank-pressure-sensor) .
Disconnect the Evaporative Emission (EVAP) purge pipe from the EVAP canister purge valve. Install a hand held vacuum gauge to the EVAP purge port. Disconnect the EVAP canister purge valve harness connector. Monitor vacuum on the vacuum gauge. Start the engine and allow the engine to idle. Increase the idle to 1200-1500 RPM. Does the vacuum gauge indicate an increase in vacuum? If yes, go to next step. If no, go to «DIAGNOSTIC AIDS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) .
Replace the EVAP canister purge valve. After repairs, go to next step.
With a scan tool, capture and record the Fail Record data and clear the DTCs. Perform the Service Bay Test. Does the scan tool indicate that the Service Bay Test passed? If yes, go to next step. If no, go to step 3 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

The EVAP system tests run when the engine is first started and meets the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . An intermittent condition could be caused by an improperly installed or damaged EVAP canister purge valve, or by a temporary blockage in the EVAP canister purge valve.

DTC P1635: 5-VOLT REFERENCE LOW

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The PCM uses the 5-volt reference 1 circuit as a sensor feed to the TP sensor, MAP sensor, EGR valve pintle position sensor and the FTP sensor.

The PCM monitors the voltage on the 5-volt reference 1 circuit. If voltage is out of tolerance, PCM will set DTC P1635.

The engine is running.

The PCM detects a voltage out of tolerance condition on the 5-volt reference 1 circuit.
The above condition is present for longer than 10 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Inspect the PCM and engine grounds. Ensure that the grounds are clean and secure. If a problem is found, repair as necessary. Did you find and correct the condition? If yes, go to step 13 . If no, go to next step.
Turn ignition off. Disconnect the EGR valve electrical connector. Turn ignition on, with engine off. Using a Digital Multimeter (DMM), measure voltage between the 5-volt reference circuit and engine ground. Does the voltage measure about 5 volts? If yes, go to step 6 . If no, go to next step.
Does the voltage measure more than 5 volts? If yes, go to step 9 . If no, go to step 7 .
Reconnect EGR valve. Disconnect TP sensor harness connector. Using a DMM, measure voltage between the TP sensor harness connector 5-volt reference 1 circuit and engine ground. Does the voltage measure about 5 volts? If yes, see «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM. If no, go to step 10 .
Monitor Digital Multimeter (DMM) while disconnecting all other devices connected to 5-volt reference circuit one at a time. If voltage changes when one of the components are disconnected, replace the component. Was a component replaced? If yes, go to step 13 . If no, go to next step.
Turn ignition off. Disconnect the PCM. Inspect the 5-volt reference circuit for a short to ground or any sensor low reference circuit. If a problem is found, repair as necessary. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 12 .
Turn ignition off. Disconnect the PCM. Turn ignition on, with engine off. Inspect the following circuits for a short to voltage: The 5-volt reference circuit, MAP sensor signal circuit, or FTP sensor signal circuit. If a problem is found, repair as necessary. Did you find and correct the condition? If yes, go to step 13 . If no, go to step 12 .
Inspect for a short between the EGR control high circuit and the 5-volt reference circuit and repair as necessary. Did you find and correct the condition? If yes, go to step 13 . If no, go to next step.
Replace the EGR valve. After repairs, go to step
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1639: 5-VOLT REFERENCE 2 CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Powertrain Control Module (PCM) uses the 5-volt reference 2 circuit as a sensor feed for the A/C refrigerant pressure sensor. The PCM monitors the voltage on the 5-volt reference 2 circuit. If the voltage is out of tolerance, the PCM will set DTC P1639.

The engine must be running.

The PCM detects a voltage out of tolerance condition on the 5-volt reference 2 circuit.
Condition is present for more than 10 seconds.

The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecutive ignition cycle, the control module records the operating conditions at the time of the failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

The control module turns OFF the Malfunction Indicator Light (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
Clear the MIL and the DTC with a scan tool.

The numbers below refer to the step numbers in the diagnostic procedures.

7 The ignition must be turned OFF and PCM powered down or test may become inaccurate.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Observe the Freeze Frame/Failure Records data for this DTC. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC or as close to the Freeze Frame/Failure Records data that you observed. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC fail this ignition? If yes, go to next step. If no, go to «INTERMITTENT CONDITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.
Inspect the PCM and engine grounds. Ensure that the grounds are clean and secure. If a problem is found, repair as necessary. Did you find and correct the condition? If yes, go to step 12 . If no, go to next step.
Turn ignition off. Disconnect the A/C pressure sensor connector, located on condenser tube. Connect a Digital Multimeter (Digital Multimeter (DMM)) between the 5-volt reference and a good ground. Turn the ignition ON, with the engine OFF. Does the voltage measure about 5 volts? If yes, go to step 10 . If no, go to next step.
Does the voltage measure more than 5 volts? If yes, go to next step. If no, go to step 7 .
Turn ignition off. Disconnect the PCM. Inspect for a short to voltage on the 5-volt reference circuit. Repair as necessary. Did you find and repair a problem? If yes, go to step 12 . If no, go to step 11 .
Turn ignition off. Using a DMM inspect for continuity between the 5-volt reference circuit and the low reference circuit at the A/C pressure sensor connector. Does the resistance measure infinity or OL? If yes, go to next step. If no, go to step 9 .
Leave the ignition OFF. Using a DMM, inspect for continuity between the 5-volt reference circuit and a good chassis ground. Does the resistance measure infinity or OL? If yes, go to step 11 . If no, go to next step.
Repair the circuit for a short to chassis ground or a short to A/C pressure sensor low reference. After repairs, go to step 12 .
Replace the A/C pressure sensor. After repairs, go to step 12 .
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

DTC P1640: DRIVER 1 INPUT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Output Driver Modules (ODM) are chips that are inside the Powertrain Control Module (PCM). The ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. The ODM 1 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the ignition 1 input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

The ignition is ON.

The ODM has detected a voltage greater than 33 volts.
Excessive current is detected on any circuit to the ODM.
The conditions are present for 30 seconds.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is DTC P0560 set? If yes, diagnose engine electrical system. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
With a scan tool, select the Output Driver Data list. Observe the parameters on the scan tool. Do any parameters indicate a fault present? If yes, go to next step. If no, go to step 5 .
Test for a short to voltage on the control circuit of the component that indicated a fault. Did you find and correct the condition? If yes, go to step 6 . If no, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

An over charging condition may set this DTC. Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Repair the circuits as necessary. If problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1650: DRIVER 2 INPUT - HIGH VOLTAGE

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Output Driver Modules (ODM) are chips that are inside the Powertrain Control Module (PCM). The ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. The ODM 2 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the battery input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

The ignition is ON.

The ODM has detected a voltage greater than 33 volts.
Excessive current is detected on any circuit to the ODM.
The conditions are present for 30 seconds.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is DTC P0560 set? If yes, diagnose engine electrical system. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
With a scan tool, select the Output Driver Data list. Observe the parameters on the scan tool. Do any parameters indicate a fault present? If yes, go to next step. If no, go to step 5 .
Test for a short to voltage on the control circuit of the component that indicated a fault. Did you find and correct the condition? If yes, go to step 6 . If no, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

An overcharging condition may set this DTC. Repair the circuits as necessary. If problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1660: COOLING FANS CONTROL CIRCUIT

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Output Driver Modules (ODM) are chips that are inside the Powertrain Control Module (PCM). The ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. The ODM 3 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the ignition 1 input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

The ignition is ON.

The ODM has detected a voltage greater than 33 volts.
Excessive current is detected on any circuit to the ODM.
The conditions are present for 30 seconds.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is DTC P0560 set? If yes, diagnose engine electrical system. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
With a scan tool, select the Output Driver Data list. Observe the parameters on the scan tool. Do any parameters indicate a fault present? If yes, go to next step. If no, go to step 5 .
Test for a short to voltage on the control circuit of the component that indicated a fault. Did you find and correct the condition? If yes, go to step 6 . If no, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use scan tool in order to clear DTCs. Turn OFF ignition for 30 seconds. Start engine. Operate vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

An overcharging condition may set this DTC. Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Repair the circuits as necessary. If problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

DTC P1670: OUTPUT DRIVER MODULE NO. 4

Note. For circuit reference, see WIRING DIAGRAMS article. For component locations, see COMPONENT LOCATIONS . For connector identification, see CONNECTOR IDENTIFICATION .

The Output Driver Modules (ODM) are chips that are inside the Powertrain Control Module (PCM). The ODMs provide grounded outputs that control devices. Each output has an internal feedback circuit that connects to the PCM microprocessor. The ODM 4 determines if the voltage or the current may cause damage to the PCM. The PCM monitors voltage through the ignition 1 input. Any incorrect current that is on a circuit to the ODM will cause the ODM to report this DTC.

The ignition is ON.

The ODM has detected a voltage greater than 33 volts.
Excessive current is detected on any circuit to the ODM.
The condition is present for 30 seconds.

The control module stores the DTC information into memory when the diagnostic runs and fails.
The Malfunction Indicator Light (MIL) will not illuminate.
The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
The driver information center, if equipped, may display a message.

A current DTC Last Test Failed clears when the diagnostic runs and passes.
A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
Clear the DTC with a scan tool.

Perform diagnostic system check - engine controls. See «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-system-check-engine-controls) under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
Is DTC P0560 set? If yes, diagnose engine electrical system. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. If no, go to next step.
With a scan tool select the Output Driver Data list. Observe the parameters on the scan tool. Do any parameters indicate a fault present? If yes, go to next step. If no, go to step 5 .
Test for a short to voltage on the circuit to the component that indicated a fault. Did you find and correct the condition? If yes, go to step 6 . If no, go to next step.
Replace PCM. Perform PCM relearn procedure. See «POWERTRAIN CONTROL MODULE»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__powertrain-control-module) under PROGRAMMING. After replacing PCM, go to next step.
Use the scan tool in order to clear the DTCs. Turn ignition off for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running the DTC. See «CONDITIONS FOR RUNNING DTC»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l) . Does the DTC run and pass? If yes, go to next step. If no, go to step 2 .
Using scan tool, observe stored information and Capture Info. Does the scan tool display any DTCs that you have not diagnosed? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/impala/viii-1999-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-34l__diagnostic-trouble-code-definitions) . If no, system is okay.

An overcharging condition may set this DTC. Thoroughly inspect any circuitry that is suspected of causing the intermittent complaint. Repair the circuits as necessary. If problem is intermittent, refer to INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

See also:
• MODEL IDENTIFICATION
• DIAGNOSTIC PROCEDURE
• DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS
• VEHICLE DATA RECORDER
• POWERTRAIN CONTROL MODULE
• DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 OR P1683: CONTROL MODULE READ ONLY MEMORY
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• INTERMITTENT CONDITIONS
• DTC P1336: CRANKSHAFT POSITION SYSTEM VARIATION NOT LEARNED
• CKP SYSTEM VARIATION LEARN PROCEDURE
• ENGINE OIL LIFE RESET
• THEFT DETERRENT PASSWORD LEARN PROCEDURE
• CONDITIONS FOR RUNNING (COLD START)
• CONDITIONS FOR RUNNING
• P0030
• P0101
• P0102
• P0103
• P0107
• P0108
• P0112
• P0113
• P0116
• P0117
• P0118
• P0121
• P0122
• P0123
• P0125
• P0128
• P0130
• P0131
• P0132
• P0133
• P0134
• P0135
• P0137
• P0138
• P0140
• P0141
• P0171
• P0172
• P0201-P0206
• P0230
• P0300
• P0325
• P0327
• P0336
• P0341
• P0401
• P0403
• P0404
• P0405
• P0420
• P0440
• P0442
• P0443
• P0446
• P0449
• P0452
• P0453
• P0506
• P0507
• P0650
• P1106
• P1107
• P1111
• P1112
• P1114
• P1115
• P1121
• P1122
• P1133
• P1134
• P1351
• P1352
• P1361
• P1362
• P1374
• P1380
• P1381
• P1404
• P1441
• P1635
• P1639
• P1640
• P1650
• P1660
• P1670
• CONDITIONS FOR RUNNING DTC
• PROGRAMMING

Engine Controls Self-Diagnostics - 3.4l Chevrolet Impala VIII

MODEL IDENTIFICATION

INTRODUCTION

ON-BOARD DIAGNOSTICS

Code Types

Freeze Frame/Failure Records

Monitors

INTERMITTENT CONDITIONS

Preliminary

Harness or Connector Intermittents

Electrical Connections or Wiring

Control Module Power & Grounds, & Component Power & Grounds

Temperature Sensitivity

Electromagnetic Interference (EMI) and Electrical Noise

Incorrect PCM Programming

Duplicating Failure Conditions

Scan Tool Snapshot

Vehicle Data Recorder

DIAGNOSTIC PROCEDURE

RETRIEVING DIAGNOSTIC TROUBLE CODES

Scheme 1

DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS

Description

Test Description

Diagnostic Procedures

CLEARING DIAGNOSTIC TROUBLE CODES

Scan Tool

Disconnect Battery

Warm-up Cycles

SCAN TOOL USAGE

PCM LOCATION

PROGRAMMING

CKP SYSTEM VARIATION LEARN PROCEDURE

ENGINE OIL LIFE RESET

POWERTRAIN CONTROL MODULE

Remote Programming

Off-Board Programming

THEFT DETERRENT PASSWORD LEARN PROCEDURE

10-Minute Learn Procedure

30-Minute Learn Procedure

DRIVE CYCLES

Conditions For Updating I/M System Status

Monitored Emission Control Systems

Diagnostic Aids

Conditions For Running (Cold Start)

Conditions For Running

SUMMARY

DIAGNOSTIC TROUBLE CODE DEFINITIONS

Scheme 2

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Scheme 33