Engine Controls - Self Diagnostics - 8.1l Chevrolet Avalanche I

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.

MODEL IDENTIFICATION

INTRODUCTION

To properly diagnose and repair this vehicle, follow DIAGNOSTIC STARTING POINT - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM. If no Diagnostic Trouble Codes (DTC) are present and a no-start condition exists, proceed to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If no DTCs are present and a driveability condition exists, diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.). Proceed to SYMPTOMS in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

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, in most cases, illuminate the Malfunction Indicator Light (MIL) located on instrument cluster.

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.

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

Code Types

There are 3 types of DTC categories

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

Freeze Frame/Failure Records

PCM stores one freeze frame record (failure record "0") 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. Six additional failure records can be stored in PCM. Failure records will be stored for all types of codes, whether or not the MIL is illuminated. If more than 6 DTCs are set, oldest DTC is deleted as newest DTC is stored. Typical failure record data includes

1. Air/fuel ratio.
2. Airflow rate.
3. Fuel trim.
4. Engine speed.
5. Engine load.
6. Engine coolant temperature.
7. Vehicle speed.
8. Throttle position angle.
9. Manifold absolute pressure.
10. Injector base pulse width.
11. Loop status.

Monitors

1. Comprehensive Component Monitor Monitors PCM systems for opens, shorts, grounds and out-of-range sensors. Also monitors rationality of sensors. Rationality is whether the sensors value is consistent with the operating conditions of the other sensors.
2. 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.
3. Fuel Trim Monitor Monitors short and long term fuel trim for being at maximum lean or rich limit.
4. Oxygen Sensor Monitor Monitors all oxygen sensors for maximum voltage level, minimum voltage level and lean rich/rich lean switching rate.
5. Oxygen Sensor Heater Monitor Monitors oxygen sensor heater by watching sensor's time-to-activity after a cold start.
6. Catalyst Monitor Monitors catalyst efficiency by comparing activity rate of precatalyst oxygen sensor and postcatalyst oxygen sensor.
7. EGR Monitor Monitors operation and flow rate of EGR system.
8. EVAP Monitor Monitors EVAP system for large leaks, small leaks and purge flow.
9. Secondary Air Monitor Monitors secondary air operation.

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

1. Vibration.
2. Engine torque.
3. Bumps or rough pavement.

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

1. Move related connectors and wiring while monitoring the appropriate scan tool data.
2. Move related connectors and wiring with the component commanded ON and OFF, with the scan tool. Observe the component operation.
3. 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

1. Data displayed.
2. Component or system operation.
3. Engine operation.

Repair the components as necessary.

Electrical Connections or Wiring

1. Intermittents are usually caused by one or more of the following conditions: Poor electrical connections. Terminal tension. Wiring problems.
2. 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.
3. Repair the condition as necessary.

Control Module Power & Grounds, & Component Power & Grounds

Poor power or ground connections can cause widely varying symptoms.

1. 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 lamp 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 POWER DISTRIBUTION in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.
2. 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 GROUND DISTRIBUTION in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

Temperature Sensitivity

1. 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.
2. The following data may help to diagnose this type of intermittent condition: Freeze Frame/Failure Records. Scan tool snapshot. Vehicle data recorder.
3. 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.
4. 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.
5. 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 electromagnetic interference (EMI) or other types of electrical noise. Perform the following procedures

1. 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.
2. 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.
3. 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.
4. Test for an open diode across the A/C compressor clutch and for other open diodes. Some relays may contain a clamping diode.
5. Test for proper performance of the generator. See ON-VEHICLE TESTING in appropriate GENERATORS & REGULATORS article in ELECTRICAL.
6. If a DTC is determined to be intermittent, and the tests in this section do not reveal a problem, see «VEHICLE DATA RECORDER»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__vehicle-data-recorder) .

Incorrect PCM Programming

1. 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.
2. 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__powertrain-control-module) under PROGRAMMING.

Duplicating Failure Conditions

1. If none of the previous tests are successful, attempt to duplicate or capture the failure conditions.
2. 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 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.
3. An alternate method is to drive the vehicle with the Digital Multimeter (DMM) connected to a suspected circuit. An abnormal reading on the DMM when the 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 the 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 STARTING POINT - ENGINE CONTROLS

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

1. 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. If no DTCs are present and a driveability problem exists, see «SYMPTOMS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. Doing so will help identify proper system or component to check in «SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l) article.
3. After necessary repairs are made, clear DTCs, verify vehicle will enter "closed loop" operation and ensure DTC does not reset.

Description

The Diagnostic System Check is an organized approach to identifying a condition that is created by a malfunction in the powertrain 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 table reduces diagnostic time, and prevents the replacement of good parts.

Test Description

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

1. 2 Lack of communication may be caused by a partial or a total malfunction of the Class 2 serial data circuit. The specified procedure determines the particular condition.
2. 6 This step stores the Powertrain Control Module (PCM) Diagnostic Trouble Code (DTC) information into the scan tool's memory. After you complete the diagnostic procedure, review the captured information in order to catch the next DTC if the control module stores multiple DTCs. Review the Freeze Frame data and the Failure Records data. Use this information in order to determine how frequently and how recently the DTC set. This information may help diagnose an intermittent condition. Information about the operating conditions at the time that the DTC set may also help diagnose an intermittent condition. Capturing the stored information saves the data that the PCM loses during the following conditions: When a diagnostic procedures instructs you to clear the DTCs. When a diagnostic procedure instructs you to disconnect the PCM connectors. When a diagnostic procedure instructs you to replace the PCM. See appropriate REMOVAL & INSTALLATION article.
3. 7 The presence of DTCs which begin with "U", indicate that some other module is not communicating. Following the specified procedure will gather all the available information before you perform the tests.
4. 9 If there are other modules with DTCs set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . 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.
5. 11 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 status that did not set.

Diagnostic Procedure

Note. Do not perform this diagnostic if there is not a driveability concern, unless another procedure directs you to this diagnostic. Before you proceed with diagnosis, search for applicable service bulletins. Unless a diagnostic procedure instructs you, do NOT clear the DTCs. If there is a condition with the starting system, see appropriate STARTERS article in ELECTRICAL. Ensure the battery has a full charge. Ensure the battery cables are clean and tight. Ensure the PCM grounds are clean, tight, and in the correct location.

1. Install a scan tool. Does the scan tool turn ON? If yes, go to next step. If no, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
2. Turn ON the ignition, with the engine OFF. Attempt to establish communication with the listed control modules. If you are using a Tech 2®, obtain the information using the Class 2 Message Monitor feature: PCM. Body Control Module (BCM). Instrument Panel (IP) cluster. Electronic Brake Control Module (EBCM). Driver Information Center (DIC). Heating, Ventilation, and Air Conditioning (HVAC). Does the scan tool communicate with all the listed control modules? If yes, go to next step. If no, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Access CLASS 2 POWER MODE in DIAGNOSTIC CIRCUIT CHECK on scan tool. Rotate ignition switch through all positions while observing IGNITION SWITCH POWER MODE parameter. Actual ignition switch position should match IGNITION SWITCH POWER MODE parameter on scan tool. (Scheme 283) Do all ignition switch positions match all IGNITION SWITCH POWER MODE parameters on scan tool? If yes, go to next step. If no, see «POWER MODE MISMATCH»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l).
4. Attempt to start the engine. Does the engine start and idle? If yes, go to next step. If no, see «SYMPTOMS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
5. Select the DTC display function for the following control modules: PCM, BCM, IP Cluster, EBCM, DIC and HVAC. Does the scan tool display any DTCs? If yes, go to next step. If no, go to step 10.
6. Using a scan tool, select CAPTURED INFO in order to store the powertrain DTC information. When complete, go to next step.
7. Does the scan tool display DTCs which begin with a "U"? If yes, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT for diagnosis. If no, go to next step.
8. Does the scan tool display DTC P0601, P0602, P0604 or P0606? If yes, see «DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 & P1683: PCM MEMORY»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__dtc-p0601-p0607-p1600-p1621-p1627-p1680) under DIAGNOSTIC TESTS. If no, go to next step.
9. Does the scan tool display DTC P0562, P0563, P1637 or P1638? If yes, see appropriate GENERATORS & REGULATORS article in ELECTRICAL. If no, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions).
10. Is the customer's concern with the automatic transmission? If yes, see appropriate DIAGNOSIS article in AUTOMATIC TRANSMISSIONS. If no, go to next step.
11. Is the customer's concern with Inspection and Maintenance (I/M) testing? If yes, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) under DRIVE CYCLES.
12. Review 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, unstable, or incorrect idle and stalling, dieseling, run-on and backfire. See «SYMPTOMS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-81l__symptoms) in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. Did you find and correct the condition? If yes, system is okay. If no, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions).

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

1. 3 Lack of communication may be due to a partial malfunction of the class 2 serial data circuit or due to a total malfunction of the class 2 serial data circuit. The specified procedure will determine the particular condition.
2. 4 Determine if the Powertrain Control Module (PCM) has DTCs set which may affect engine cooling operation.
3. 5 The presence of DTCs which begin with "U" indicate some other module is not communicating. The specified procedure will compile all the available information before tests are performed.

1. The Diagnostic System Check will provide the following information: The identification of the control module(s) which command the system. The ability of the control module(s) to communicate through the serial data circuit. The identification of any stored Diagnostic Trouble Codes (DTCs) and their status. The use of the Diagnostic System Check will identify the correct procedure for diagnosing the system and where the procedure is located.
2. Install a scan tool. Does the scan tool turn ON? If yes, go to next step. If no, see SCAN TOOL DOES NOT POWER UP in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
3. Turn ON the ignition, with the engine OFF. Attempt to establish communication with the PCM. If you are using a Tech 2®, obtain the information using the Class 2 Message Monitor feature. Does the scan tool communicate with the PCM? If yes, go to next step. If no, see SCAN TOOL DOES NOT COMMUNICATE WITH CLASS 2 DEVICE in appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT.
4. Select the Powertrain Control Module display DTCs function on the scan tool. Does the scan tool display any DTCs? If yes, go to next step. If no, see «COOLING SYSTEM TROUBLE SHOOTING»(/chevrolet/avalanche/i-2001-2006/remont/basic-trouble-shooting/#basic-trouble-shooting-general-information__cooling-system-trouble-shooting) under ENGINE MECHANICAL in TROUBLE SHOOTING - BASIC PROCEDURES article in GENERAL INFORMATION.
5. Does the scan tool display DTCs which begin with a "U"? If yes, see appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT for diagnosis. If no, go to next step.
6. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) .

Note. On vehicles that have several control modules connected by serial data circuits, one module is the Power Mode Master (PMM). On vehicles covered in this article, the PMM is the Body Control Module (BCM). The BCM uses 3 signals from the ignition switch. These are the Ignition 0, Ignition 1, and Accessory.

Normal vehicle class 2 communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by the BCM in order to determine the correct power mode. The BCM communicates the system power mode to all class 2 modules on the class 2 serial data line.

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

1. 6 This step tests for battery voltage on the signal circuits that are not required.
2. 7 This step tests for no battery voltage on the required signal circuits.
3. 8 If any ignition switch parameters that should be inactive in the present ignition switch position are active, 2 ignition switch signal circuits may be shorted together.
4. 9 This step eliminates open circuits as the cause of the malfunction.

Note. This procedure is used if the observed vehicle power mode does not match the actual ignition switch position. Open the driver's door and leave it open during this test. This will disable the RAP power mode and eliminate this power mode from the power mode parameter list.

1. Connect a scan tool to Data Link Connector (DLC). Turn OFF the ignition. Using a scan tool, under the DIAGNOSTIC CIRCUIT CHECK menu, observe the CLASS 2 POWER MODE parameter. Does the displayed power mode parameter match the actual ignition switch position? If yes, go to next step. If no, go to step 6 .
2. Turn the ignition switch to the UNLOCK position. Using a scan tool, under the DIAGNOSTIC CIRCUIT CHECK menu, observe the CLASS 2 POWER MODE parameter. Does the displayed power mode parameter match the actual ignition switch position? If yes, go to next step. If no, go to step 6 .
3. Turn ON the ignition, with the engine OFF. Using a scan tool, under the DIAGNOSTIC CIRCUIT CHECK menu, observe the CLASS 2 POWER MODE parameter. Does the displayed power mode parameter match the actual ignition switch position? If yes, go to next step. If no, go to step 6 .
4. Turn the ignition switch to the CRANK position. Using a scan tool, under the DIAGNOSTIC CIRCUIT CHECK menu, observe the CLASS 2 POWER MODE parameter. Does the displayed power mode parameter match the actual ignition switch position? If yes, go to next step. If no, go to step 6 .
5. Turn the ignition switch to the ACCY position. Using a scan tool, under the DIAGNOSTIC CIRCUIT CHECK menu, observe the CLASS 2 POWER MODE parameter. Does the displayed power mode parameter match the actual ignition switch position? If yes, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) . If no, go to next step.
6. Turn OFF the ignition. Disconnect the BCM. Hold the ignition switch in the position that indicated the incorrect power mode. Using a test light connected to a good ground, test the BCM ignition switch inputs for voltage. See BODY CONTROL MODULES in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Is voltage present on only the inputs specified for the ignition switch position? If yes, go to next step. If no, go to step 8 .
7. Hold the ignition switch in the position that indicated the incorrect power mode. Using a test light connected to a good ground, test the BCM ignition switch inputs for voltage. See BODY CONTROL MODULES in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. If voltage does not exist on any inputs specified for the ignition switch position, go to step 9 . If voltage exists on any inputs specified for the ignition switch position, go to step 11 .
8. Disconnect the ignition switch. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. Test the BCM ignition switch input circuits for a short to voltage. Test the BCM ignition switch circuits for a short between circuits. See BODY CONTROL MODULES in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 10 .
9. Disconnect the ignition switch. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. Test the BCM ignition switch input circuits for an open. See BODY CONTROL MODULES in appropriate SYSTEM WIRING DIAGRAMS article in ELECTRICAL. Did you find and correct the condition? If yes, go to step 14 . If no, go to next step.
10. Inspect for poor connections and terminal tension at the harness connector of the ignition switch. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 12 .
11. Inspect for poor connections and terminal tension at the harness connector of the BCM. Did you find and correct the condition? If yes, go to step 14 . If no, go to step 13 .
12. Replace the ignition switch. See appropriate STEERING COLUMN SWITCHES article in ACCESSORIES & EQUIPMENT. After ignition switch replacement, go to step 14 .
13. Replace the BCM. See appropriate BODY CONTROL MODULES article in ACCESSORIES & EQUIPMENT. After BCM replacement, go to next step.
14. Reconnect all disconnected components and connectors. Using a scan tool, under the DIAGNOSTIC CIRCUIT CHECK menu, observe the CLASS 2 POWER MODE parameter. Cycle the ignition switch through all possible positions, one at a time. Does the displayed power mode parameter match the actual ignition switch position? If yes, system is okay. If no, go to step 1 .

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). See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS . DLC is located below left side of dash.

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.

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.

POWERTRAIN CONTROL MODULE LOCATION

Powertrain Control Module (PCM) is located in left front corner of engine compartment. See COMPONENT LOCATIONS .

CRANKSHAFT POSITION SENSOR

Note. The Crankshaft Position (CKP) system variation learn procedure is required when the following service procedures have been performed, regardless of whether DTC P0315 is set: CKP sensor replacement. Engine replacement. PCM replacement. Harmonic balancer replacement. Crankshaft replacement. Any engine repairs which disturb the CKP sensor relationship. For additional diagnostic information, see DTC P0315: CRANKSHAFT POSITION SENSOR VARIATION NOT LEARNED .

1. Install a scan tool to Data Link Connector (DLC).
2. With a scan tool, monitor the powertrain control module for DTCs. If only DTC P0315 is set, go to next step. If a DTC other than P0315 is set, diagnose that DTC first. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) .
3. With a scan tool, select the CRANKSHAFT POSITION VARIATION LEARN PROCEDURE.
4. The scan tool instructs you to perform the following: Accelerate to Wide Open Throttle (WOT). Release when the fuel cut-off occurs. The engine should not accelerate beyond calibrated RPM value. Release the throttle immediately if the value is exceeded. Block the drive wheels. Set the parking brake. DO NOT apply the brake pedal. Cycle the ignition from OFF to ON. Apply and hold the brake pedal. Start and idle the engine. Turn the A/C OFF. The vehicle must remain in Park or Neutral. 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: Crankshaft Position (CKP) sensors activity. If there is a CKP sensor condition, refer to the applicable DTC that set. Camshaft Position (CMP) sensor activity. If there is a CMP sensor condition, refer to the applicable DTC that set. Engine Coolant Temperature (ECT). If the ECT is not warm enough, idle the engine until the ECT reaches the correct temperature.
5. Enable the crankshaft position system variation learn procedure with the scan tool.
6. Accelerate to WOT.
7. Release when the fuel cut-off occurs.
8. The scan tool displays Learn Status: Learned this ignition. If the scan tool indicates that DTC P0315 ran and passed, the CKP variation learn procedure is complete. If the scan tool indicates DTC P0315 failed or did not run, refer to «DTC P0315: CRANKSHAFT POSITION SENSOR VARIATION NOT LEARNED»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) . If any other DTCs set, refer to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) for the applicable DTC that set.
9. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.

ENGINE OIL LIFE RESET

The engine oil life monitor will indicate when to change the engine oil - usually between 3,000 miles (5 000 km) and 10,000 miles (16 000 km) since the last oil change. Under severe conditions, the CHANGE OIL SOON light may be displayed before 3,000 miles (5 000 km). The vehicle must not be driven more than 10,000 miles (16 000 km) or 12 months without an oil change. Reset the oil life monitor when the oil has been changed, use the following procedure.

1. Press fuel button until Engine Oil Life appears on screen.
2. Press and hold select button for five seconds.
3. OIL LIFE RESET will appear for 10 seconds.
4. The system is reset.

POWERTRAIN CONTROL MODULE

Note. Service of the PCM should normally consist of either replacement of the PCM or EEPROM programming. If the diagnostic procedures call for the PCM to be replaced, the PCM should be checked first to see if it is the correct part. If it is, remove the faulty PCM and install the new service PCM. The service PCM EEPROM will not be programmed. DTC P0601 and P0602 indicates the EEPROM is not programmed or has malfunctioned.

Note. Programing Powertrain Control Module requires a compatible scan tool and a Techline® terminal. Procedure uses a Tech 2® scan tool.

Remote 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.

1. Connect the Tech 2® to the vehicle and obtain the module information using the following procedure: NOTE: Ensure the control module is installed in the vehicle and the battery is fully charged before programming. Connect the Tech 2® to the vehicle data link connector (DLC), with the engine and the Tech 2® OFF. Turn ON the Tech 2®. Press Enter at the title screen. Turn ON the ignition, with the engine OFF. Select Service Programming System at the Main Menu. NOTE: Select Request Info Again if a vehicle identification number (VIN) was previously stored in the Tech 2®. Select Request Info. Enter the vehicle description by following the on-screen instructions. Turn OFF all accessories and select Continue. NOTE: Select No and write down the VIN if the VIN is incorrect. Verify that the correct VIN is entered on the Tech 2® and select Yes.
2. Turn OFF the Tech 2®.
3. Disconnect the Tech 2® from the vehicle.
4. Turn OFF the ignition.
5. Transfer the data from the terminal to the Tech 2® using the following procedure: Connect the Tech 2® to the terminal. NOTE: The TIS supports service programming with the Tech 2® scan tool only. Launch the TIS application at the terminal. Select the Service Programming System at the main screen. Highlight the following information on the Select Diagnostic Tool and Programming Process Screen: Select Diagnostic Tool--Select Tech 2®. Select Programming Process--Identify whether an existing module is being reprogrammed or a module is being replaced with a new one. Select ECU Location--Select vehicle. Select Next. Verify the connections and select Next. NOTE: You may receive a message stating that the control module could be a service control module if you selected NO to the VIN being correct. Click OK. Verify the VIN and select Next. Select the appropriate controller for the vehicle being serviced. NOTE: When selecting the Vehicle Configuration Index (VCI) programming type, a valid VCI number for the vehicle must be entered. This number may be obtained from the Techline® Customer Support. Select the type of programming to be performed from the following categories: Normal--Used for updating an existing calibration or programming a new controller. Vehicle configuration index (VCI)--Used for updating an existing controller or programming a new controller for newer vehicles whose VINs are not yet in the database. Reconfigure--Used to reconfigure a vehicle for changes in tire size and axle ratios. Select Next. NOTE: Refer to Service bulletins before service programming is performed if the bulletins are listed along with the calibration files. Select the appropriate calibration file for the vehicle being serviced. Select Next. NOTE: Select Cancel if you receive a message stating that the calibration selected is already the current calibration in the control module and reprogramming with the same download is not allowed. Verify your selection on the Summary screen. Select Next.
6. Perform the Crankshaft Position Variation Relearn Procedure using the Special Functions feature, if applicable.
7. Close the application and return to the TIS application Selection screen after the download is complete.
8. Turn OFF the Tech 2®.
9. Disconnect the Tech 2® from the terminal.
10. Transfer the data from the Tech 2® to the control module using the following procedure: Connect the Tech 2® to the vehicle DLC, with the engine and the Tech 2® OFF. Turn ON the Tech 2®. Press Enter at the Title screen. Turn ON the ignition, with the engine OFF. Select Service Programming System. Select the Program ECU function on the Tech 2®. Verify the VIN and calibration numbers, select Continue. Follow the on-screen instructions and select Continue. Select continue and exit the program after the Tech 2® displays Programming was Successful.
11. Turn OFF the ignition.
12. Turn OFF the Tech 2®.
13. Disconnect the Tech 2® from the vehicle.
14. Verify the control module programming was successful using the following procedure: Turn OFF the ignition for 30 seconds. NOTE: Repeat the SPS procedure if the vehicle does not start or starts but runs rough. Start the engine.

Off-Board Remote Programming

Note. The Off-Board Programming Adapter Kit (J 41207-C) is required when a module must be programmed without having the vehicle present. The adapter allows the module to be turned ON and communicate with the scan tool.

1. Obtain the vehicle identification number (VIN) of the vehicle for which the module is being programmed.
2. Launch the TIS application at the terminal.
3. Select the Service Programming System.
4. Highlight the following information on the Select Diagnostic Tool and Programming Process screen: Select Diagnostic Tool-Select Tech 2®. Select Programming Process-Identify whether an existing module is being reprogrammed or replaced with a new one. Select ECU location-select Off-Board Programming Adapter.
5. Select Next.
6. Follow the directions on the Preparing for Communication screen for connecting the following components: The control module. The Off-Board Programming Adapter (OBPA)--Refer to the TIS Users Guide for a listing of the OBPA. The Tech 2®.
7. Select the Service Programming Request Information function on the Tech 2®.
8. Follow the Tech 2® instructions to obtain the module data and security information.
9. After the Tech 2® has received the data from the module, exit the Request Info mode.
10. Connect the Tech 2® to the terminal.
11. Turn ON the Tech 2®.
12. Select Next at the terminal after the Tech 2® start-up screen appears.
13. Enter the VIN of the vehicle that will be receiving the control module.
14. Select Next.
15. Select the type of programming to be performed from the following categories: Normal--Used for updating an existing calibration or programming a new controller. Vehicle configuration index (VCI)--Used for updating an existing controller or programming a new controller for newer vehicles whose VINs are not yet in the database. Reconfigure--Used to reconfigure a vehicle for changes in tire size and axle ratios.
16. Select Next.
17. Select a calibration on the Calibration Selection screen, if necessary.
18. Ensure all the desired folder tabs have a green check mark.
19. Select Next.
20. Verify the current and the selected calibration of the control module on the Summary screen.
21. Select Next.
22. Select OK.
23. On model year 1996 and newer controllers, a crankshaft position (CKP) relearn procedure box may appear. Select OK.
24. Follow the on-screen instructions, if any, when the Program Controller/Programming Complete screen appears.
25. Select Close.
26. Turn OFF the Tech 2®.
27. Disconnect the Tech 2® from the terminal.
28. Connect the Tech 2® to the OBPA.
29. Turn ON the Tech 2®.
30. Select Enter at the title screen.
31. Select the Service Programming System at the Main Menu.
32. Select the Program ECU function.
33. Select Continue.
34. Follow the on-screen instructions.
35. Select Continue.
36. Select Exit when the programming is complete.
37. Turn OFF the OBPA.
38. Turn OFF the Tech 2®.
39. Disconnect the OBPA from the Tech 2® and the control module.

Off-Board Pass-Thru Programming

Note. The Off-Board Programming Adapter Kit (J 41207-C) is required when a module must be programmed without having the vehicle present. The adapter allows the module to be turned ON and communicate with the scan tool.

1. Launch the TIS application at the terminal.
2. Select the SERVICE PROGRAMMING SYSTEM.
3. Highlight the following information on the Select Diagnostic Tool and Programming Process Screen: Select Diagnostic Tool--Select Pass-Thru. Select Programming Process--Identify whether an existing module is being reprogrammed or a module is being replaced with a new one. Select ECU Location--Select vehicle.
4. Select Next.
5. Complete all terminal-directed data at the Preparing for Communication/Determine Vehicle screen until Next is highlighted.
6. Select Next.
7. Follow the on-screen instructions for connecting the following components: The control module. The Off-Board Programming Adapter (OBPA)--Refer to the TIS Users Guide for a listing of OBPA. The Tech 2®.
8. Select Next.
9. Pass-Thru displays the VIN stored in the control module. If a new control module is being programmed, enter the correct VIN of the vehicle.
10. Select Next.
11. Select the appropriate options if the Options screen appears.
12. Select Next.
13. Select the type of programming to be performed from the following categories: Normal--Used for updating an existing calibration or programming a new controller. Vehicle Configuration Index (VCI)--Used for updating an existing controller or programming a new controller for newer vehicles whose VINs are not yet in the database. Reconfigure--Used to reconfigure a vehicle for changes in tire size and axle ratios.
14. Select Next.
15. Select a calibration selection on the Calibration Selection screen, if necessary.
16. Ensure all the desired calibration folder tabs have a green check mark.
17. Select Next.
18. Verify the current and selected calibration of the control module on the Summary screen.
19. Select Next.
20. Select OK.
21. Select OK.
22. When programming is complete, a Program Controller/Programming Complete screen appears. Follow the on-screen instructions, if any.
23. Select Close.
24. Turn OFF the OBPA.
25. Turn OFF the scan tool.
26. Disconnect the OBPA from the Tech 2® and the control module.

Pass-Thru Programming

Note. Pass-Thru programming allows the scan tool to remain connected to the terminal and to the vehicle throughout the programming process. The vehicle must be in close proximity to the terminal while using Pass-Thru.

1. Launch the TIS application at the terminal.
2. Select the SERVICE PROGRAMMING SYSTEM.
3. Highlight the following information on the Select Diagnostic Tool and Programming Process Screen: Select DIAGNOSTIC TOOL, then select PASS-THRU. Select PROGRAMMING PROCESS. Identify whether an existing module is being reprogrammed or a module is being replaced with a new one. Select ECU LOCATION. Select VEHICLE.
4. Select Next.
5. Complete all terminal-directed data on the Preparing for Communication/Determine Vehicle screen until Next is highlighted.
6. Select Next.
7. Follow the instructions on the Preparing for Communication screen.
8. Select Next.
9. Verify the VIN on the Validate Vehicle Identification Number screen.
10. Select Next.
11. If an option screen appears, verify the vehicle configuration and/or RPO information.
12. Select Next.
13. Highlight the appropriate control module and programming type on the Supported Controllers screen.
14. Select Next.
15. Select the proper calibrations on the Calibration Selection screen.
16. Ensure all the folder tabs have a green check mark.
17. Select Next.
18. Verify the current calibrations with the selected calibrations.
19. Select Next.
20. The Transfer Data screen will appear until the progress bar reaches 100 percent. This may take up to 30 minutes.
21. Complete all of the terminal-directed data on the Programming Complete screen.
22. Turn OFF the Tech 2®.
23. Disconnect the Tech 2® from the vehicle.

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® 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

1. Passlock® Sensor
2. BCM
3. PCM

10-Minute Learn Procedure

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

1. Connect the Tech 2® to the vehicle.
2. Select "REQUEST INFORMATION" under "SERVICE PROGRAMMING".
3. Disconnect the Tech 2® from the vehicle and connect it to a Techline® terminal.
4. On the Techline® terminal, select "THEFT MODULE RE-LEARN" under "SERVICE PROGRAMMING".
5. Disconnect the Tech 2® from the Techline® terminal and connect it to the vehicle.
6. Turn ON the ignition, with the engine OFF.
7. Select "PROGRAM ECU" under "SERVICE PROGRAMMING".
8. Attempt to start the engine, then release the key to ON (vehicle will not start).
9. Observe the SECURITY telltale, after approximately 10 minutes the telltale will turn OFF (the vehicle is now ready to relearn the Passlock® Sensor Data Code and/or password on the next ignition switch transition from OFF to CRANK).
10. Turn OFF the ignition, and wait 5 seconds.
11. Start the engine (the vehicle has now learned the password).
12. With the Tech 2® (scan tool), clear any DTCs.

30-Minute Learn Procedure

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

DRIVE CYCLES

See INSPECTION/MAINTENANCE SYSTEM CHECK .

Several states require that a vehicle pass on-board diagnostic (OBD) system tests and the I/M emission inspection in order to renew license plates. This is accomplished by viewing the I/M System Status display on a scan tool. Using a scan tool, the technician can observe the I/M System Status in order to verify that the 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 Malfunction Indicator Lamp (MIL). Once all of the tests are complete, the I/M System Status display will indicate YES in the Completed column. For example, when the Heated Oxygen Sensor (HO2S) Heater Test indicates YES, all of the oxygen sensor heaters have been diagnosed. If the vehicle has four heated oxygen sensors, all four 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

1. The vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
2. The battery has been disconnected or discharged below operating voltage.
3. The control module power or ground has been interrupted.
4. The control module has been reprogrammed.
5. 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 secondary Air Injection (AIR) or Exhaust Gas Recirculation (EGR). The OBD-II regulations require monitoring of the following

1. Air conditioning system.
2. Catalytic converter efficiency.
3. Comprehensive component monitoring. Emission related inputs and outputs.
4. Evaporative (EVAP) emissions system.
5. Exhaust Gas Recirculation (EGR) system.
6. Fuel delivery system.
7. Heated catalyst monitoring.
8. Misfire monitoring.
9. Oxygen sensor system (O2S or HO2S).
10. Oxygen sensor heater system (HO2S heater).
11. Secondary Air Injection (AIR) system.

For the specific DTCs required for each system, see

INSPECTION/MAINTENANCE SYSTEM DTCS

table. 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.

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

1. 1 Any DTCs set, even those that are not listed in the INSPECTION/MAINTENANCE SYSTEM DTCS table, 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. 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. 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.

Procedure

1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) 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.
2. 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 reprogramming or repair service required? If yes, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) . If no, go to next step.
3. With a scan tool, observe the I/M System Status display. Is more than one test indicating a NO status? If yes, see «INSPECTION/MAINTENANCE COMPLETE SYSTEM SET PROCEDURE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) . If no, go to the I/M 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, the failure indication 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 table because this 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.

The purpose of the I/M Complete System Set Procedure is to satisfy the enable criteria necessary to execute all of the I/M readiness diagnostics, and complete the trips for those particular diagnostics. When all diagnostic tests are complete, the I/M System Status indicators are set to YES. Perform this test when more than one or all of the I/M System Status indicators are set to NO.

Conditions for Running

Cold Start

1. The Barometric (BARO) pressure is more than 74 kPa.
2. The Engine Coolant Temperature (ECT) is below 86°F (30°C).
3. The Intake Air Temperature (IAT) is below 86°F (30°C).
4. The difference between the Intake Air Temperature (IAT) and the Engine Coolant Temperature (ECT) is 14°F (8°C) or less.
5. The battery voltage is between 9-18 volts.
6. The fuel level is between 1/4 and 3/4.

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

1. 1 Make sure that you perform the Inspection/Maintenance System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2 This step runs the HO2S Heater Tests and initiates 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: Engine Coolant Temperature (ECT) less than 86°F (30°C). ECT and Intake Air Temperature (IAT) are within 14°F (8°C) of each other at start-up.
3. 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. 4 This step runs the Exhaust Gas Recirculation (EGR) Tests. The EGR 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.
5. 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. 6 Perform the individual system test for any of the systems that do not update to YES.
7. 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.

1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure that the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Set the vehicle parking brake. Verify that the transmission is in Park for automatic transmissions and Neutral for manual transmissions. Start the engine and allow the engine to idle. Allow the engine to idle for 2 minutes. When complete, go to next step.
3. In order for the next group of tests to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 55 MPH with this speed maintained until the engine reaches operating temperature. This may be up to 8-10 minutes depending on the start up coolant temperature. Continued operation under these conditions for an additional 6 minutes. After procedure, go to next step.
4. In order for the next group of tests to run, the vehicle must operate in the following conditions: Vehicle speed 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 transmission. NO clutch actuation on a manual transmission. NO manual downshift. The vehicle speed remains above 25 MPH. After each deceleration period, the vehicle is returned to 45 MPH under part throttle acceleration and the speed is maintained for 15 seconds. When complete, go to next step.
5. In order for the next group of tests to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 45-55 MPH with this speed maintained for 2 minutes. Deceleration to 0 MPH. Engine idling for 2 minutes while the following criteria is maintained: Service brake depressed. Automatic transmission in drive. Manual transmission in neutral with the clutch pedal depressed. When complete, go to next step.
6. 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.
7. 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, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__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 Heated Oxygen Sensor (HO2S) Heater and Evaporative (EVAP) emission 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 the 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 EVAP, secondary Air Injection (AIR), and HO2S tests. The procedure instructs the technician to operate the vehicle in the enable conditions for 6 minutes. If all 3 tests have updated to YES within 4 minutes, it is not necessary to continue with the enable conditions and testing can advance to the next step.

INSPECTION/MAINTENANCE SYSTEM DTCS

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

1. The Barometric (BARO) pressure is more than 74 kPa.
2. The engine coolant is at operating temperature, 160-248°F (71-120°C).
3. The Intake Air Temperature (IAT) is between 5-167°F (-15 to 75°C).
4. The engine is in Closed Loop fuel control.
5. The engine has run for 6-8 minutes off idle in order to initiate test.
6. The battery voltage is between 11-18 volts.

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

1. 1 Make sure that you perform the Inspection/Maintenance System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 2 Perform the Catalyst Test during the idle period immediately following the cruise period.
3. 3 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. See «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. 4 This step helps identify any unique or unusual criteria required to run the diagnostic test if the universal set procedure does not. This information is located in Conditions for Running DTC.
5. 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.

1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Start the engine and allow the engine to idle. For this test to run, the vehicle must operate in the following conditions: Acceleration at part throttle to 55 MPH with this speed maintained for 8 minutes. Deceleration to 0 MPH. Engine idling for 2 minutes while the following criteria is maintained: Service brake depressed. Automatic transmission in Drive. Manual transmission in Neutral with the clutch pedal depressed. With a 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.
3. With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, go to next step.
4. To determine which DTCs are required to run in order to complete this test, see «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) table. 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 DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat procedure for any additional required DTCs that have not run. With a scan tool, observe the I/M System Status display. Did the Catalyst System Status update to YES? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
5. 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, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__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 Lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs). 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 in order to execute the I/M readiness diagnostics for the Evaporative (EVAP) emission system. The test may be used in order to set the I/M System Status indicators to YES. The I/M System Status Display on the scan tool provides an indication of when the control module has completed the required tests. The I/M System Status does not indicate that the tests have passed or failed. When all of the diagnostics for a specific system have run and passed and 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 other tests for that system have not run. Performing a visual inspection prior to running the EVAP test may prevent having to repeat the test. A failed or aborted test will require the vehicle to cool down in order to meet the enable criteria to run another test.

1. DTCs P0442, P0446, P0455, P0496 are not set.
2. The barometric pressure is more than 75 kPa.
3. The fuel level is between 1/4 and 3/4.
4. The battery voltage is between 10-18 volts.
5. The Engine Coolant Temperature (ECT) is between 39-86°F (3.8-30°C).
6. The Intake Air Temperature (IAT) is between 39-86°F (3.8-30°C).
7. The difference between the ECT and the IAT is less than 14°F (8°C).

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 cooling fan or an A/C compressor clutch turning ON may cause the test to abort.

1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. Ensure that the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Start the engine and idle. To run this test, the vehicle must operate in the following conditions: Acceleration at part throttle to 45 MPH with this speed maintained until the 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. Deceleration to 0 MPH. Engine idling for 2 minutes. Turn OFF the ignition for one hour. After one hour, turn ON the ignition. Using scan tool, observe EVAP system status. Did the EVAP System Status update to YES? If yes, go to step 5 . If no, go to next step.
3. With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, go to next step.
4. To determine which DTCs are required to run in order to complete this test, see «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) table. 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 DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat this procedure 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
5. 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, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, system is okay.

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

1. The Engine Coolant Temperature (ECT) is more than 135°F (57°C).
2. The engine is running in Closed Loop fuel control.
3. The engine has been running for more than 160 seconds.
4. The battery voltage is between 10-18 volts.

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 Lamp (MIL) is requested. The I/M System Status also registers the number of diagnostic trouble codes (DTCs). 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 numbers below refer to the step numbers on the procedure.

1. 1 Make sure that you perform the Inspection/Maintenance System Check before performing this test. Failure to do so may result in difficulty updating the status to YES.
2. 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. 3 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. See «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. 4 This step helps identify any unique or unusual criteria required to run the diagnostic test if the universal set procedure does not. This information is located in Conditions for Running DTC.
5. 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.

1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. Ensure that the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories (e.g., A/C, blower fan, etc.). Start the engine and allow it to idle. To run this test, the vehicle must operate in the following conditions: Acceleration at part throttle to 45-55 MPH with this speed maintained for 6 minutes or until the I/M System Status updates to YES. Manual transmissions, 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.
3. With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, go to next step.
4. To determine which DTCs are required to run in order to complete this test, see «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) table. 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 DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat this procedure for any additional required DTCs that have not run. With a scan tool, observe the 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
5. 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, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, system is okay.

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Heated Oxygen Sensor (HO2S) system. The test may be used to set the I/M System Status to YES. Ensure the vehicle meets the requirements listed in Conditions for Running before performing this test. If you do not meet the necessary requirements, test results may be inaccurate.

1. The start up Engine Coolant Temperature (ECT) is more than 140°F (60°C).
2. The battery voltage is between 10-18 volts.

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, the test may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent the HO2S heater test from initiating.

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 Lamp (MIL) is requested. The I/M System Status also registers the number of Diagnostic Trouble Codes (DTCs).

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, maintain necessary enable conditions until the system status updates to YES.

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

1. 1 Make sure that you perform the I/M System Check before performing this test. If you do not, the I/M System Check may result in difficulty updating the status to YES.
2. 2 Preprogramming the scan tool will reduce the amount of time the oxygen sensor heaters operate while verifying the enable criteria.
3. 3 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. See «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. 4 This step helps identify any unique or unusual criteria required to run the diagnostic test if the universal set procedure does not. This information is located in Conditions for Running DTC.
5. 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.

1. Did you perform the Inspection/Maintenance (I/M) System Check? If yes, go to next step. If no, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. Preprogram the scan tool with the vehicle information before the ignition is turned ON. Ensure the vehicle is within the Conditions for Running specified in the supporting text. Set the vehicle parking brake. Verify the transmission is in Park for automatic transmissions and Neutral for manual transmissions. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine and allow it to idle. Allow the engine to idle for 2 minutes 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.
3. With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, go to next step.
4. To determine which DTCs are required to run in order to complete this test, see «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) table. 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 DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat this procedure for any additional required DTCs that have not run. With a scan tool, observe the I/M System Status display. Did the HO2S Heater System Status update to YES? If yes, go to next step. If no, see «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
5. 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, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, system is okay.

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Exhaust Gas Recirculation (EGR) 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. Failure to meet the necessary requirements may produce inaccurate test results.

1. The Barometric Pressure (BARO) is more than 70 kPa.
2. The engine coolant has exceeded 140°F (60°C).
3. The Intake Air Temperature (IAT) is between 32-212°F (0-100°C).

The control module only runs the EGR Active Tests during a gradual deceleration with a closed throttle and a vehicle speed above 25 MPH (40 km/h). Several deceleration cycles may be necessary in order to accumulate a sufficient number of EGR flow samples. The procedure outlined in the table 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, it may take more than three deceleration cycles to complete the test. 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 Lamp (MIL) is requested. The I/M System Status also registers the number of Diagnostic Trouble Codes (DTCs).

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, maintain necessary enable conditions until the system status updates to YES.

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

1. 1 Make sure that 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. 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. 3 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/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. 4 This step helps identify unique or unusual criteria required to run the diagnostic test if the universal set procedure does not run. This information is located in the service information under Conditions for Running the DTC.
5. 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.

1. Did you perform the Inspection/Maintenance (I/M) System Check? If YES, go to next step. If NO, see «INSPECTION/MAINTENANCE SYSTEM CHECK»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
2. In order for this test to run, the vehicle must operate in the following conditions: Ensure the vehicle is within the Conditions for Running specified in the supporting text. Turn OFF all of the accessories, e.g., A/C, blower fan, etc. Start the engine and allow it to idle. Acceleration at part throttle to 80 km/h (50 mph) with this speed maintained for 1 minute. Four decelerations of 25 seconds each from 80 km/h (50 mph) while the following criteria is maintained: The throttle is closed. NO brake application on either manual or automatic transmission. NO clutch actuation on a manual transmission. NO manual downshift. The vehicle speed remains above 25 mph (40 km/h). After each deceleration period, the vehicle is returned to 50 mph (80 km/h) under part throttle acceleration and the 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.
3. With a scan tool, observe the DTC Information. Does the scan tool indicate any failed DTCs? If yes, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, go to next step.
4. Refer to «INSPECTION/MAINTENANCE SYSTEM DTCS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) to determine which DTCs are required to run in order to complete this test. 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, located in the supporting text for the diagnostic table of the DTC. Repeat the procedure until the scan tool indicates the diagnostic test has run. Repeat steps 4-6 for any additional required DTCs that have not run. With a 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, see «DIAGNOSTIC AIDS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
5. 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, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__diagnostic-trouble-code-definitions) . If no, system okay.

SUMMARY

If no Diagnostic Trouble Codes (DTCs) are present and a no-start condition exists, proceed to NO-START DIAGNOSIS in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article. If no DTCs are present and a driveability condition exists, diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.). See SYMPTOMS in TROUBLE SHOOTING - NO CODES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE INDEX

Scheme 283

Scheme 284

Scheme 285

Scheme 286

Scheme 287

Scheme 288

Scheme 289

Scheme 290

Scheme 291

Scheme 292

Scheme 293

Scheme 294

Scheme 295

Scheme 296

Scheme 297

Scheme 298

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Scheme 300

Scheme 301

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Scheme 303

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Scheme 308

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Scheme 310

Scheme 311

Scheme 312

Scheme 313

Scheme 314

Scheme 315

Scheme 316

Scheme 317

Scheme 318

Scheme 319

Scheme 320

Scheme 321

Scheme 322

Scheme 323

Scheme 324

Scheme 325

Scheme 326

Scheme 327

Scheme 328

Scheme 329

Scheme 330

Scheme 331

Scheme 332

Scheme 333

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Scheme 337

Scheme 338

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Scheme 340

Scheme 341

Scheme 342

MALFUNCTION INDICATOR LAMP

Note. Information is not available from manufacturer.

DIAGNOSTIC TESTS

Note. Before clearing DTCs, perform powertrain diagnostic system check. 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. If PCM is replaced, NEW PCM must be programmed using special manufacturer's equipment. See POWERTRAIN CONTROL MODULE under PROGRAMMING.

DTC P0101: MASS AIR FLOW SENSOR PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Mass Air Flow (MAF) sensor is an air flow 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 all 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 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 2,000 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

1. The Manifold Absolute Pressure (MAP).
2. The Intake Air Temperature (IAT).
3. The engine speed (RPM).

The PCM compares the actual MAF sensor frequency signal to the predicted MAF value. This comparison will determine 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.

Conditions For Running DTC

1. Trucks Only DTCs P0401, P0404, or P0405 are not set.
2. DTCs P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0120, P0220, P0442, P0443, P0446, P0449, P0455, P0496, or P2135 are not set.
3. The engine is cranking or running.
4. The ignition 1 signal is between 11 volts and 18 volts.
5. The Throttle Position (TP) sensor angle is less than 95 percent.
6. The change in the TP sensor angle is less than 5 percent.
7. The MAP sensor is less than 80 kPa.
8. The change in the MAP sensor is less than 3 kPa.
9. The above conditions are met for 1.5 seconds.

Conditions For Setting DTC

The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 4 seconds.

Action Taken When DTC Sets

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

Conditions For Clearing MIL/DTC

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

Inspect for the following conditions

1. An incorrectly routed harness. Inspect the harness of the MAF sensor in order to verify that it is not routed too close to the following components: The secondary ignition wires or coils. Any solenoids. Any relays. Any motors.
2. 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.
3. Inspect for any contamination or debris on the sensing elements of the MAF sensor.
4. Inspect the air induction system for any water intrusion. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set.
5. A Wide Open Throttle (WOT) acceleration from a stop should cause the MAF sensor g/s display on the scan tool to increase rapidly. This increase should be from 7-12 g/s at idle to 230 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.
6. A high resistance of 15 ohms or more on the ignition 1 voltage circuit may cause this DTC to set. A high resistance may cause a driveability concern before this DTC sets.
7. 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. 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 1000 feet (305 meters) of altitude.
8. A high resistance on the 5-volt reference circuit of the MAP sensor may cause this DTC to set.
9. A high resistance on the low reference circuit of the MAP sensor may cause this DTC to set.
10. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 This step will determine if the MAP sensor pressure is within the proper range for a given altitude.
2. 6 This step will determine if the MAP sensor voltage is within the proper range at idle.
3. 7 This step will determine if the MAP sensor responds properly to the change in manifold pressure.
4. 8 This step will determine if the TP sensors are operating properly.
5. 9 This step will determine if any mechanical faults have caused this DTC to set.
6. 10 This voltage drop test will determine if high resistance has caused this DTC to set.

Scheme 343

Scheme 344

ALTITUDE VERSUS BAROMETRIC PRESSURE

DTC P0102: MASS AIR FLOW SENSOR CIRCUIT - LOW FREQUENCY

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Mass Air Flow (MAF) sensor is an air flow 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 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 2,000 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.

1. The engine is running for more than 2 seconds.
2. The engine speed is more than 400 RPM.
3. The ignition 1 signal is more than 8 volts.
4. The MAF sensor frequency is stable for more than one second.

The PCM detects that the MAF sensor frequency signal is less than 1300 Hz.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Inspect for the following conditions

1. Inspect the harness of the MAF sensor to verify that it is not routed too close to the following components: The secondary ignition wires or coils. Any solenoids. Any relays. Any motors. Any aftermarket accessories.
2. A low minimum air rate through the sensor bore at idle or during deceleration may cause this DTC to set. Inspect for any vacuum leak downstream of the MAF sensor.
3. Inspect for any contamination or debris on the sensing elements of the MAF sensor.
4. A wide open throttle acceleration from a stop should cause the MAF sensor g/s parameter on the scan tool to increase rapidly. This increase should be from 7-12 g/s at idle to 230 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.
5. Truck Only A high resistance of 15 ohms or more on the ground circuit of the MAF sensor may cause this DTC to set. A high resistance may cause a driveability concern before this DTC sets.
6. A high resistance of 15 ohms or more on the ignition 1 voltage circuit can cause this DTC to set. A high resistance may cause a driveability concern before this DTC sets.
7. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 This step will determine if any mechanical faults have caused this DTC to set.
2. 7 This voltage drop test will determine if high resistance has caused this DTC to set.
3. 9 This step verifies the signal circuit from the MAF sensor electrical connector to the PCM.
4. 10 This step tests the signal circuit of the MAF sensor for a short to another 5-volt reference circuit.
5. 11 This step will determine if the PCM is able to process the frequency signal that it receives from the MAF sensor.
6. 14 This step will determine which portion of the circuit or which component is shorted to ground.
7. 17 This step verifies that the signal circuit is not shorted to any other PCM circuit.

Scheme 345

Scheme 346

Scheme 347

DTC P0103: MASS AIR FLOW SENSOR CIRCUIT - HIGH FREQUENCY

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Mass Air Flow (MAF) sensor is an air flow 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 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 2,000 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 MAF sensor.

1. The engine is running.
2. The engine speed is more than 400 RPM.
3. The ignition 1 signal is more than 8 volts.
4. The MAF sensor parameter is stable for more than 0.7 second.

The PCM detects that the MAF sensor frequency signal is more than 12,000 Hz.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. Inspect the air induction system for any water intrusion. The water rapidly cools the hot sensing elements in the sensor causing a false indication of excessive air flow. Any water that reaches the MAF sensor will skew the sensor and may cause this DTC to set.
2. A poor connection in the ignition 1 voltage circuit of the MAF sensor may cause this DTC to set.
3. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 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 at the PCM. Disconnecting the MAF sensor may set additional related DTCs.
2. 4 This step will determine if incorrect harness routing has caused this DTC to set.
3. 5 This step will determine if water intrusion has caused this DTC to set.

Scheme 348

DTC P0106: MAP SYSTEM PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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

1. 5-volt reference circuit.
2. Low reference circuit.
3. MAP 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 (BARO) pressure. 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.

The PCM calculates a predicted value for the MAP sensor based on throttle position and engine speed. The PCM then compares the predicted value to the actual MAP sensor signal. The DTC P0106 will set if the MAP sensor signal is not within the predicted range.

1. DTC P0101, P0102, P0103, P0107, P0108, P0120, P0220, P0401, P0404, P0405, P0442, P0443, P0446, P0455, P1125, P1514, P1515, P1516, P1518, P2108, P2120, P2121, P2125, P2126, P2130, P2131, P2135 are not set.
2. The engine speed is between 400-5,000 RPM.
3. The change in engine speed is less than 125 RPM.
4. Traction control, if equipped, is not active.
5. The A/C compressor clutch is steady.
6. The power steering is stable.
7. The power take-off (PTO), if equipped, is not active.
8. The clutch switch state does not change, if equipped with a manual transmission.
9. The brake switch state does not change.
10. The above conditions are met for 1 second.

The PCM detects that the MAP sensor voltage is not within the predicted range for 1.5 seconds.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 4 This step tests the MAP sensors ability to correctly indicate Barometric (BARO) pressure.
2. 6 This step tests the MAP sensors ability to respond to an increase in engine vacuum.
3. 8 This step tests for a proper MAP sensor pressure with an applied vacuum.

Scheme 349

Scheme 350

Scheme 351

DTC P0107: MAP SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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

1. 5-volt reference circuit.
2. Low reference circuit.
3. MAP 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 intake 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 (BARO) pressure. 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 the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 will set.

1. DTC P0120, P0220, P1125, P1514, P1515, P1516, P1518, P2108, P2120, P2121, P2125, P2126, P2130, P2131, P2135 are not set.
2. The engine is running.
3. The throttle angle is zero percent when the engine speed is less than 800 RPM, or the throttle angle is more than 12.5 percent when the engine speed is more than 800 RPM.

The PCM detects that the MAP sensor voltage is less than 0.10 volt for more than 2 seconds.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 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 can help to locate an intermittent condition.

Scheme 352

Scheme 353

DTC P0108: MAP SENSOR CIRCUIT - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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

1. 5-volt reference circuit.
2. Low reference circuit.
3. MAP 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 intake 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 (BARO) pressure. 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 the PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 will set.

1. DTC P0120, P0220, P1125, P1514, P1515, P1516, P1518, P2108, P2120, P2121, P2125, P2126, P2130, P2131, P2135 are not set.
2. Engine is running for a length of time that is determined by the start-up coolant temperature. The length of time ranges from 4 minutes at less than -22° F (-30° C) to 30 seconds at more than 86° F (30° C).
3. The throttle angle is less than one percent when the engine speed is less than 1,200 RPM, or the throttle angle is less than 20 percent when the engine speed is more than 1,200 RPM.

The PCM detects that the MAP sensor voltage is more than 4.9 volts for more than 2 seconds.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The Powertrain Control Module (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.

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

The number below refers to the step number in the diagnostic procedure.

1. 3 Operate the vehicle within the same conditions as when the DTC failed. If you cannot duplicate the DTC, use the information included in the Freeze Frame/Failure Records data in order to locate an intermittent condition

Scheme 354

Scheme 355

DTC P0112: IAT SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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.

1. DTCs P0502, P0503 are not set.
2. The engine run time is more than 45 seconds.
3. The Vehicle Speed Sensor (VSS) indicates that vehicle speed is more than 25 MPH.

The IAT is more than 262°F (128°C) for 5 seconds.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The PCM 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 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.

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

1. When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other.
2. If an intermittent condition exists, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 356

Scheme 357

DTC P0113: IAT SENSOR CIRCUIT - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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.

1. DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0125, P0128, P0502, P0503 are not set.
2. The engine run time is more than 120 seconds.
3. The Vehicle Speed Sensor (VSS) indicates that vehicle speed is less than 7 MPH.
4. The Engine Coolant Temperature (ECT) is more than 140°F (60°C).
5. The Mass Air Flow (MAF) is less than 15 g/s.

The PCM detects that the IAT Sensor parameter is less than -38°C (-36°F) for more than 5 seconds.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. When the vehicle is at ambient temperature the IAT sensor and ECT sensor temperatures should be relatively close to each other.
2. 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.
3. If an intermittent condition exists, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 6 This step tests for the proper operating 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.

Scheme 358

Scheme 359

DTC P0116: ECT SENSOR PERFORMANCE (SIERRA & SILVERADO)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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 and a ground for the ECT low reference circuit. When the ECT is low, the sensor resistance is high. When the ECT is high, the sensor resistance is low. The PCM uses this input for engine controls and enabling criteria for diagnostics. The internal clock of the PCM will record the amount of time the ignition is OFF. At restart the PCM will compare the temperature difference between the ECT and the Intake Air Temperature (IAT). Before failing this test the PCM will perform a calculation to determine the presence of a block heater. If the PCM detects that the temperature difference is not within the calibrated amount after the ignition OFF time, DTC P0116 sets.

1. The ignition is ON.
2. DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, P0602, P1621, P1683 are not set.
3. The vehicle has a minimum ignition OFF time of 10 hours.

If the PCM detects a temperature difference between the ECT sensor and the IAT sensor of more than 27°F (15°C), then the vehicle must be driven for more than 400 seconds over 15 mph. If the IAT sensor temperature decreases more than 5°F (3°C), a block heater is detected and the test is aborted. If the IAT sensor temperature does not decrease, a block heater was not detected and DTC P0116 sets.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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 control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

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

1. DTC P0116 is designed to detect a ECT sensor that is skewed high.
2. An IAT sensor that is skewed low could cause this DTC to set.
3. When testing the ECT sensor or the IAT sensor, the Temperature Vs Resistance table should be used to determine if a skewed sensor is the problem. See «TEMPERATURE VS. RESISTANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .

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

1. 3 This step tests for excessive resistance in the ECT sensor circuit.
2. 4 This step tests for excessive resistance in the IAT sensor circuit.
3. 8 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Scheme 360

Scheme 361

TEMPERATURE VS. RESISTANCE

DTC P0116: ECT SENSOR PERFORMANCE (AVALANCHE, SUBURBAN & YUKON XL)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

The Intake Air Temperature (IAT) sensor is a variable resistor. 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 and a ground for the IAT low reference circuit. When the IAT sensor is cold, the sensor resistance is high. When the air temperature increases, the sensor resistance decreases. 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.

1. DTCs P0101, P0102, P0103, P0116, P0117, P0118, P0125, P0128, P0502, P0503 are not set.
2. The engine run time is more than 120 seconds.
3. The Vehicle Speed Sensor (VSS) indicates that the vehicle speed is less than 7 MPH.
4. The Engine Coolant Temperature (ECT) is more than 140° F (60° C).
5. The Mass Air Flow (MAF) is less than 15 g/s.

The PCM detects that the IAT sensor parameter is less than -36° F (-38° C) for more than 5 seconds.

1. The Powertrain Control Module (PCM) illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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 control module writes the operating conditions to the Freeze Frame and updates the Failure Records.

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

1. DTC P0116 is designed to detect a ECT sensor that is skewed high.
2. An IAT sensor that skewed low could cause this DTC to set.
3. When testing the ECT sensor or the IAT sensor, the Temperature Vs Resistance table should be used to determine if a skewed sensor is the problem. See «TEMPERATURE VS. RESISTANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .

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

1. 3 This step tests for excessive resistance in the ECT sensor circuit.
2. 4 This step tests for excessive resistance in the IAT sensor circuit.
3. 8 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Scheme 362

Scheme 363

Scheme 364

Scheme 365

DTC P0117: ECT SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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, this Diagnostic Trouble Code (DTC) will set.

The engine run time is more than 10 seconds; or, the engine run time is less than 10 seconds when IAT is less than 122°F (50°C).

The ECT sensor temperature is more than 282°F (139°C) for more than 20 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

Conditions For Clearing MIL or DTC

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

1. An overheating condition may cause this DTC to set.
2. After starting the engine, the ECT sensor temperature should rise steadily to about 194°F (90°C) then stabilize after the thermostat opens.
3. 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. See «TEMPERATURE VS. RESISTANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. If an intermittent condition exists, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 366

DTC P0118: ECT SENSOR CIRCUIT - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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 and a ground for the ECT low reference 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 has been running for more than 60 seconds; or, the engine run time is less than 60 seconds when the Intake Air Temperature (IAT) is more than 32°F (0°C).

The ECT sensor temperature is less than -36°F (-38°C) for 20 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. If a short to a separate 5-volt source occurs, this DTC may set.
2. After starting the engine, the ECT should rise steadily then stabilize after the thermostat opens.
3. Use the Temperature vs. Resistance 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. See «TEMPERATURE VS. RESISTANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. If an intermittent condition exists, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 367

Scheme 368

DTC P0120: TP SENSOR CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

The Throttle Position (TP) sensor 1 is a potentiometer type sensor with 3 circuits

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The TP sensor is used to determine the throttle plate angle for various engine management systems. The control module provides the TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensor then provides the control module a signal voltage proportional to throttle plate movement. TP sensor 1 signal voltage is low at closed throttle and increases as the throttle opens. When the control module detects that the TP sensor 1 signal or TP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

1. DTCs P1518 or P2108 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is more than 5.23 volts.

1. The TP sensor 1 signal voltage is less than 0.37 volt or more than 4.51 volts.
2. The above condition is present for more than 1 second.

1. The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power Mode.
4. Under certain conditions the control module commands the engine OFF.
5. The message center displays Reduced Engine Power.

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

1. Inspect the Throttle Actuator Control (TAC) module connectors for signs of water intrusion. When this occurs, multiple DTCs could be set with no circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.
3. If this DTC is determined to be intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 33 When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the may redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture info.

Scheme 369

Scheme 370

Scheme 371

Scheme 372

DTC P0125: EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROL (SIERRA & SILVERADO)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The 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.

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 the Closed Loop temperature. If the coolant temperature does not increase normally or does not reach Closed Loop temperature, the diagnostics that use engine coolant temperature as enabling criteria may not run when expected.

This DTC will only run once per ignition cycle within the enabling conditions. If the PCM detects the calibrated amount of air flow and engine run time have been met and the ECT has not met the Closed Loop temperature, DTC P0125 sets.

1. DTCs P0101, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0500, P0502, P0503, P1111, P1112, P1114, or P1115 are not present.
2. The engine run time is between 120-1400 seconds.
3. The minimum air temperature is 19° F (-7° C).
4. The start-up coolant temperature is less than 104°F (40°C).
5. The Mass Air Flow (MAF) average is more than 20 g/s.
6. The vehicle speed is more than 5 MPH for more than 0.5 mi.
7. This diagnostic has not previously run this ignition cycle.

1. The PCM detects that the calibrated amount of engine run time has been met.
2. The calibrated amount of engine air flow has been met.
3. The engine coolant temperature for Closed Loop of 113° F (45° C) has not been met.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

DTC P0125 is designed to detect a skewed ECT sensor or a faulty thermostat.

Excessive coolant flow through the by-pass hose to the throttle body may cause this DTC to set.

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

1. 3 This step tests for excessive resistance in the ECT circuit.
2. 7 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Scheme 373

Scheme 374

The 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.

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 Closed Loop temperature. If the coolant temperature does not increase normally or does not reach Closed Loop temperature, the diagnostics that use engine coolant temperature as enabling criteria may not run when expected.

This DTC will only run once per ignition cycle within the enabling conditions. If the PCM detects the calibrated amount of air flow and engine run time have been met and the ECT has not met the Closed Loop temperature, DTC P0125 sets.

1. DTCs P0101, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0500, P0502, P0503 are not present.
2. The engine run time is between 120-1400 seconds.
3. The minimum air temperature is more than 19° F (-7° C).
4. The start-up coolant temperature is less than 104° F (40° C).
5. The Mass Air Flow (MAF) average is more than 20 g/s.
6. The vehicle speed is more than 5 MPH for more than 0.5 miles.
7. The diagnostic has not previously run this ignition cycle.

The PCM detects all of the following conditions

1. The calibrated amount of engine run time has been met.
2. The calibrated amount of engine air flow has been met.
3. The calibrate vehicle speed and distance have been met.
4. The engine coolant temperature for Closed Loop of 113° F (45° C) has not been met.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Scheme 375

Scheme 376

DTC P0128: ECT LESS THAN THERMOSTAT REGULATING TEMPERATURE (SIERRA & SILVERADO)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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 Diagnostic Trouble Code (DTC) will only run once per ignition cycle within the enabling conditions. If the engine coolant fails to reach a preset target temperature before a calculated air flow is accumulated, DTC P0128 will set.

1. DTCs P0101, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0125, P0500, P0502, P0503, P1111, P1112, P1114, or P1115 are not present.
2. The start-up engine coolant temperature is less than 165°F (74°C).
3. The Air Intake Temperature (IAT) sensor is 19°F (-7°C) or more.
4. The engine is running more than 2 minutes and less than 27 minutes.
5. The vehicle speed is more than 5 MPH for more than 1.5 miles.
6. The mass airflow (MAF) average reading is more than 20 g/s.
7. The diagnostic has not previously run this ignition cycle.

1. The calibrated amount of engine run time has been met.
2. The calibrated amount of engine air flow has been met.
3. The calibrated minimum engine coolant temperature of 174° F (79° C) has not been met.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. A DTC P0128 is designed to detect a faulty thermostat.
2. Excessive coolant flow through the by-pass hose to the throttle body may cause this DTC to set.
3. A skewed ECT sensor may cause a P0128 to set.

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

1. 3 This step tests for excessive resistance in the ECT circuit.
2. 7 This step tests for a skewed sensor through the range of temperatures affecting this DTC.

Scheme 377

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 Diagnostic Trouble Code (DTC) will only run once per ignition cycle within the enabling conditions. If the engine coolant fails to reach a preset target temperature before a calculated air flow is accumulated, DTC P0128 will set.

1. DTCs P0101, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0125, P0500, P0502, P0503 are not present.
2. The start-up engine coolant temperature is less than 165°F (74°C).
3. The Air Intake Temperature (IAT) sensor is 19°F (-7°C) or more.
4. The engine is running more than 2 minutes and less than 27 minutes.
5. The vehicle speed is more than 5 MPH for more than 1.5 miles.
6. The mass airflow (MAF) average reading is more than 20 g/s.
7. The diagnostic has not previously run this ignition cycle.

The PCM detects all of the following conditions

1. The calibrated amount of engine run time has been met.
2. The calibrated amount of engine air flow has been met.
3. The calibrated vehicle speed and distance have been met.
4. The calibrated minimum engine coolant temperature of 174°F (79°C) has not been met.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Scheme 378

Scheme 379

DTC P0131: HO2S CIRCUIT - LOW VOLTAGE - BANK 1, SENSOR 1 & DTC P0151: HO2S CIRCUIT - LOW VOLTAGE - BANK 2, SENSOR 1

Note. For HO2S identification (Scheme 381)

Scheme 380

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensor (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects an HO2S voltage that stays below a specified value, DTCs P0131 or P0151 will set.

Lean Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108 or P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The TP indicated angle parameter is between 3-70 percent more than the value observed at idle.

Power Enrichment Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1514, P1515, P1516, P1518, P2108 or P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The engine run time parameter is more than 30 seconds.
6. The power enrichment parameter is active for more than 2 seconds.

Lean Test

1. The HO2S voltage is less than 200 mV for 165 seconds.

Power Enrichment Test

1. The HO2S voltage is less than 400 mV for 10 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.
3. The control module commands Open Loop.

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

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

1. 2 If the voltage is varying above and below the specified value the condition is not present.

Scheme 381

Scheme 382

DTC P0132: HO2S CIRCUIT - HIGH VOLTAGE - BANK 1, SENSOR 1 & DTC P0152: HO2S CIRCUIT - HIGH VOLTAGE - BANK 2, SENSOR 1

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensor (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects an HO2S voltage that stays below a specified value, DTCs P0131 or P0151 will set.

Rich Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108, or P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The TP indicated angle parameter is between 3-70 percent more than the value observed.

Decel Fuel Cut-Off Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1514, P1515, P1516, P1518, P2108, or P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The engine run time parameter is more than 30 seconds.
6. The Decel. Fuel Cutoff parameter is active for more than 4 seconds.

Rich Test

1. The HO2S voltage is more than 900 mV for 165 seconds.

Decel Fuel Cut-Off Test

1. The HO2S voltage is more than 250 mV for 5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.
3. The control module commands Open Loop.

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

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

1. 2 If the voltage is above and below the specified value the condition is not present.

Scheme 383

Scheme 384

Scheme 385

DTC P0133: HO2S CIRCUIT - SLOW RESPONSE - BANK 1, SENSOR 1 & DTC P0153: HO2S CIRCUIT - SLOW RESPONSE - BANK 2, SENSOR 1

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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 in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. the Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. The PCM monitors the rich-to-lean and lean-to-rich transition time. A transition is defined as, the HO2S voltage changes from above 600 mV to below 250 mV or from below 250 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0133 or P0153 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0117, P0116, P0118, P0120, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108 or P2135 are not set.
2. The Engine Coolant Temperature (ECT) sensor is more than 140°F (60°C).
3. The Evaporative (EVAP) emissions purge solenoid command is more than 1 percent.
4. The mass airflow (MAF) sensor is between 29-55 g/s.
5. The engine speed is between 1000-3000 RPM.
6. The TP Indicated Angle parameter is 5 percent more than the value observed at idle.
7. The loop status is closed.
8. The ignition 1 signal is between 10-18 volts.
9. The fuel tank level remaining is more than 10 percent.
10. The engine run time is more than 160 seconds.
11. The above conditions are met for 100 seconds.

The rich-to- lean or lean-to-rich average response time is more than a calibrated value.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 If the voltage is varying above and below the specified value, the condition is not present.

Scheme 386

Scheme 387

DTC P0134 & P0154: HO2S CIRCUIT - INSUFFICIENT ACTIVITY - BANK 1 & 2, SENSOR 1

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content in the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mv that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects that the HO2S voltage remains within the bias voltage range, DTCs P0134 or P0154 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108 or P2135 are not set.
2. The engine run time is more than 300 seconds.
3. The ignition 1 signal is between 10-18 volts.

The PCM detects that the affected HO2S voltage parameter is between 350-550 mV for 60 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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 failure. The control module writes the operating conditions to the Freeze Frame and updates the Failure Records.
3. The control module commands Open Loop.

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

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

1. 3 If the HO2S voltage is varying outside the specified range, the condition is not present.

Scheme 388

Scheme 389

DTC P0135: HO2S HEATER CIRCUIT - BANK 1, SENSOR 1, DTC P0141: HO2S HEATER CIRCUIT - BANK 1, SENSOR 2, DTC P0155: HO2S HEATER CIRCUIT - BANK 2, SENSOR 1 & DTC P0161: HO2S HEATER CIRCUIT - BANK 2, SENSOR 2

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Heated Oxygen Sensor (HO2S) must reach operating temperature to provide an accurate voltage signal. A heating element inside the HO2S minimizes the time required for the sensor to reach operating temperature. Voltage is provided to the heater by the ignition 1 voltage circuit through a fuse. With the engine running, ground is provided to the heater by the HO2S heater low control circuit, through a low side driver within the Powertrain Control Module (PCM). The PCM commands the heater ON or OFF to maintain a specific HO2S operating temperature range. The PCM determines the temperature by measuring the current flow through the heater. When the heater is in the ON state, the PCM will pulse the heater OFF for a duration of 50 ms, once per second. The PCM also monitors the current flow through the heater for diagnosis. This diagnostic will only run once per ignition cycle. If the PCM detects that the current is above or below a specified range, DTC P0135, P0141, P0155 or P0161 sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108 or P2135 are not set.
2. The ECT Sensor parameter is more than 122°F (50° C).
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The MAF sensor parameter is between 3-40 g/s.
5. The engine speed parameter is between 500-3000 RPM.
6. The engine run time parameter is more than 120 seconds.

1. The PCM detects that the affected HO2S Heater current parameter is more than 3.125 amps or less than 0.25 amps.
2. The above condition is met for 10 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 7 With no fault present, the test lamp will blink once per second.

Scheme 390

Scheme 391

DTC P0137: HO2S CIRCUIT - LOW VOLTAGE - BANK 1, SENSOR 2 & DTC P0157: HO2S CIRCUIT - LOW VOLTAGE - BANK 2, SENSOR 2

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensors (O2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects an HO2S voltage that stays below a specified value, DTCs P0137 or P0157 will set.

Lean Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108, P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The TP indicated angle parameter is between 3-70 percent more than the value observed at idle.

Power Enrichment Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108, P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The engine run time parameter is more than 30 seconds.
6. The power enrichment parameter is active for more than 2 seconds.

Lean Test

1. The HO2S voltage is less than 80 mV for 200 seconds.

Power Enrichment Test

1. The HO2S voltage is less than 490 mV for 10 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 If the voltage does not change more than the specified value, the condition is present.

Scheme 392

Scheme 393

Scheme 394

DTC P0138: HO2S CIRCUIT - HIGH VOLTAGE - BANK 1, SENSOR 2 & DTC P0158: HO2S CIRCUIT - HIGH VOLTAGE - BANK 2, SENSOR 2

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensors (O2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects an HO2S voltage that stays below a specified value, DTCs P0138 or P0158 will set.

Rich Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108, or P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The TP indicated angle parameter is between 3-70 percent more than the value observed at idle.

Decel Fuel Cut-Off Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108, or P2135 are not set.
2. The loop status is closed.
3. The ignition 1 signal is between 10-18 volts.
4. The fuel tank level remaining is more than 10 percent.
5. The engine run time parameter is more than 30 seconds.
6. The Decel. Fuel Cutoff parameter is active for more than 4 seconds.

Rich Test

1. The PCM detects that the affected HO2S voltage parameter is more than 950 mV for 200 seconds.

Decel Fuel Cut-Off Test

1. The PCM detects that the affected HO2S voltage parameter is more than 250 mV for 5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 If the voltage does not change more than the specified value, the condition is present.

Scheme 395

Scheme 396

Scheme 397

DTC P0140: HO2S CIRCUIT - INSUFFICIENT ACTIVITY - BANK 1, SENSOR 2 & DTC P0160: HO2S CIRCUIT - INSUFFICIENT ACTIVITY - BANK 2, SENSOR 2

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensors (O2S) are used for fuel control and post catalyst monitoring. Each HO2S compares the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. If the PCM detects an HO2S voltage that stays below a specified value, DTCs P0140 or P0160 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0141, P0161, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108 or P2135 are not set.
2. The engine run time is more than 300 seconds.
3. The loop status is closed.
4. The ignition 1 signal is between 10-18 volts.

1. The HO2S signal voltage is steady between 410-490 mV for 150 seconds.
2. The Throttle Position (TP) changes more than 5 percent within 1 second, 6 times.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 3 If the voltage is varying above and below the specified value, the condition is not present.

Scheme 398

Scheme 399

DTC P0171: FUEL TRIM SYSTEM LEAN - BANK 1 & DTC P0174: FUEL TRIM SYSTEM LEAN - BANK 2

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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 O2S inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, fuel trim values will be above 0 percent. If the O2S indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the heated oxygen sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustment s in order to maintain an air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, DTC P0171 or P0174 sets.

1. DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0300, P0420, P0430, P0442, P0443, P0446, P0449, P0506, or P0507 are not set.
2. The Engine Coolant Temperature (ECT) is between 167-239°F (75-115°C).
3. The Intake Air Temperature (IAT) is between 4-194° F (-20-90° C).
4. The Manifold Absolute Pressure (MAP) is between 3.7-13 psi (26-90 kPa).
5. The vehicle speed is less than 85 mph (137 km/h).
6. The engine speed is between 400-3000 RPM.
7. The Barometric pressure (BARO) is more than 10.7 psi (74 kPa).
8. The Mass Airflow (MAF) is between 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The Throttle Position (TP) is less than 90 percent.

1. The average long term fuel trim cell value is above 23 percent.
2. All of the above conditions are present for 6 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. The system will go lean if an injector is not supplying enough fuel.
2. A lean condition could be present during high fuel demand.
3. Using a scan tool, review the Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 If conditions were not corrected, check fuel system. See «FUEL SYSTEMS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-81l) in BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
2. 6 If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failures may be at fault.

Scheme 400

Scheme 401

DTC P0172: FUEL TRIM SYSTEM RICH - BANK 1 & DTC P0175: FUEL TRIM SYSTEM RICH - BANK 2

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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 oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim, fuel delivery adjustments. If the oxygen sensors indicate a lean condition, fuel trim values will be above 0 percent. If the oxygen sensors indicate a rich condition, fuel trim values will be below 0 percent. Short term fuel trim values change rapidly in response to the Heated Oxygen Sensor (HO2S) voltage signals. Long term fuel trim makes coarse adjustments in order to maintain an 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 (EVAP) emission canister is causing a rich condition. If the PCM detects an excessively rich condition, this Diagnostic Trouble Code (DTC) will set.

1. DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0420, P0430, P0442, P0443, P0446, P0449, P0506, or P0507 are not set.
2. The Engine Coolant Temperature (ECT) is between 167-239°F (75-115°C).
3. The Intake Air Temperature (IAT) is between 4-194°F (-20 to 90°C).
4. The Manifold Absolute Pressure (MAP) is between 26-90 kPa.
5. The vehicle speed is less than 85 MPH.
6. The engine speed is between 400-3000 RPM.
7. The Barometric (BARO) pressure is more than 74 kPa.
8. The Mass Airflow (MAF) is between 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The Throttle Position (TP) is less than 90 percent.

1. The average long term fuel trim value is below -13 percent.
2. All of the above conditions are present for 40 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. Fuel contamination, such as water or alcohol, will effect fuel trim.
2. A malfunctioning MAF sensor can cause a rich condition and set this DTC. See «DTC P0101: MASS AIR FLOW SENSOR PERFORMANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__dtc-p0101-mass-air-flow-sensor) .
3. Using a scan tool, review the Failure Records. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 If conditions were not corrected, see «BASIC DIAGNOSTIC PROCEDURES - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures-81l) article.
2. 6 If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical conditions may exist.

Scheme 402

Scheme 403

DTC P0200: FUEL INJECTOR CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The control module enables the appropriate fuel injector on the intake stroke for each cylinder. Ignition voltage is supplied to the fuel injectors. The control module controls each fuel injector by grounding the control circuit via a solid state device called a driver. The control module monitors the status of each driver. If the control module detects an incorrect voltage for the commanded state of the driver, a fuel injector control DTC sets.

1. The engine speed is more than 400 RPM.
2. The ignition voltage is between 6-18 volts.

1. The PCM detects an incorrect voltage on the fuel injector control circuit.
2. The condition exists for 5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. Performing the Fuel Injector Coil test may help isolate an intermittent condition. See «FUEL INJECTOR COIL TEST»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-system-component-testing-81l__fuel-injector-coil-test) under FUEL SYSTEMS in SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL article.
2. For an intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 4 This step tests for voltage at the fuel injector harness connector. The INJ fuse supplies power to the coil side of the fuel injector harness connector. If the B+ supply circuit is indicated.
2. 5 This step verifies that the PCM is able to control the fuel injector. If the lamp blinks, then the PCM and wiring are OK.
3. 6 This step tests if a ground is constantly being applied to the fuel injector.

Scheme 404

Scheme 405

DTC P0220: THROTTLE POSITION SENSOR 2 CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

The Throttle Position (TP) sensor 2 is a potentiometer type sensor with 3 circuits

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The TP sensor is used to determine the throttle plate angle for various engine management systems. The control module provides the TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensor then provides the control module a signal voltage proportional to throttle plate movement. TP sensor 1 signal voltage is low at closed throttle and increases as the throttle opens. When the control module detects that the TP sensor 2 signal or the TP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

1. DTCs P1518 or P2108 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is more than 5.23 volts.

1. The TP sensor 2 voltage is less than 0.28 volt or greater than 4.60 volts.
2. The above condition is present for more than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. Under certain conditions the control module commands the engine OFF.
5. The message center displays Reduced Engine Power.

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

1. Inspect the Throttle Actuator Control (TAC) module connectors for signs or water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTC. Remember this if you review the stored information in Capture Info.
3. For an intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 31 When the TAC module detects a condition within the TAC system, more than one TAC system related DTC may set. This is due to the may redundant tests run continuously on this system. Locating and repairing one individual condition may correct more than one DTC. Disconnecting components during testing may set additional DTCs. Keep this in mind when reviewing the stored information, Capture Info.

Scheme 406

Scheme 407

Scheme 408

Scheme 409

DTC P0230: FUEL PUMP CONTROL RELAY CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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.

1. The engine speed is more than 400 RPM.
2. The ignition voltage is between 6-18 volts.

1. The PCM detects that the commanded state of the driver and the actual state of the control circuit do not match.
2. The above conditions are present for a minimum of 2.5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 Listen for a click when the fuel pump relay operates. Command both the ON and OFF states. Repeat the commands as necessary.
2. 4 This step verifies that the PCM is providing voltage to the fuel pump relay.
3. 5 This step tests for an open in the ground circuit to the fuel pump relay.
4. 6 This step determines if voltage is constantly being applied to the control circuit of the fuel pump relay.

Scheme 410

Scheme 411

DTC P0300: ENGINE MISFIRE DETECTED

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) uses information from the crankshaft position (CKP) sensor and the camshaft position (CMP) sensor in order to determine when an engine misfire is occurring. By monitoring 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 three-way catalytic converter damage. The Malfunction Indicator Lamp (MIL) will flash ON and OFF when the conditions for catalytic converter damage are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0116, P0117, P0118, P0125, P0128, P0220, P0315, P0335, P0336, P0341, P0343, P0721, P0722, P1114, P1115, P1120, or P1258 are not set.
2. The engine speed is between 450-5000 RPM.
3. The ignition voltage is between 10-18 volts.
4. The Engine Coolant Temperature (ECT) is between 19-266°F (-7 to 130°C).
5. The fuel level is more than 10 percent.
6. The Throttle Position (TP) sensor angle is steady within 1 percent.
7. The anti-lock brake system (ABS) and the traction control system are not active.
8. The transmission is not changing gears.
9. The A/C clutch is not changing states.
10. The PCM is not in fuel shut-off or Decel Fuel Cut-Off (DFCO) mode.
11. The PCM is not receiving a rough road signal.

The PCM is detecting a crankshaft rotation speed variation indicating a misfire sufficient to cause emission levels to exceed mandated standards.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. Excessive vibration from sources other than the engine can cause a misfire DTC. The following are possible sources of vibration: Variable thickness brake rotor. Drive shaft not balanced. Worn or damaged accessory drive belt.
2. There may be more or less cylinders actually misfiring than indicated by the scan tool.
3. Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.
4. If there are multiple misfires on only one bank, inspect the fuel injector and ignition coil, power and ground circuits for that bank.

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

1. 2 If the CKP variations are not within the learned values, the misfire counters may increment.
2. 3 DTC P0135 or P0155 can be set because of a misfire.

Scheme 412

Scheme 413

Scheme 414

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 variation. 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 indicated that the CKP system variation values have not been stored in the PCM and the CKP system variation learn procedure must be performed.

DTCs P0335, P0336, P0341, P0342, or P0343 are not set.

The Engine Coolant Temperature (ECT) is more than 158° F (70° C).

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

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. 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.

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

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 P0315 is set.

1. An engine replacement.
2. A PCM replacement.
3. A harmonic balancer replacement.
4. A crankshaft replacement.
5. Any engine repairs which disturb the CKP sensor relationship.

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

1. A damaged reluctor wheel.
2. Excessive crankshaft runout.
3. A damaged crankshaft.
4. Interference in the signal circuit of the CKP sensor.
5. A coolant temperature that is not within the Conditions For Running DTC.
6. 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 P0315.

Scheme 415

DTC P0325: KNOCK SENSOR MODULE CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Knock Sensor (KS) produce an AC signal when specific frequencies are detected. When the engine operates, the Powertrain Control Module (PCM) learns a minimum and maximum frequency of noise of normal engine operation. The KS system monitors both KS in order to determine if knock is present. If the KS system determines that excessive knock is present, the PCM retards the spark timing based on the signals from the KS system. The PCM then retards timing until no knock is present.

1. The engine is running.
2. The engine run time is more than 10 seconds.
3. The ignition voltage is more than 10 volts.

A malfunction with the KS system or the circuits within the PCM are faulty for 15 seconds or more.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Scheme 416

DTC P0327: KNOCK SENSOR CIRCUIT - LOW VOLTAGE - SENSOR 1 & DTC P0332: KNOCK SENSOR CIRCUIT - LOW VOLTAGE - SENSOR 2

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Knock Sensors (KS) produce and AC signal when specific frequencies are detected. When the engine operates, the Powertrain Control Module (PCM) learns a minimum and maximum frequency of noise of normal engine operation. The KS system monitors both knock sensors in order to determine if knock is present. If the KS system determines that excessive knock is present, the PCM retards the spark timing based on the signals from the KS system. The PCM then retards the timing until no knock is present. When the PCM detects a frequency that is less than or more than a defined range, DTC P0327 will sent for a failure in KS 1 which is located on bank 1 on the drivers side of the engine or DTC P0332 will set for a failure in KS 2 which is located on bank 2 on the passenger side of the engine.

1. DTCs P0106, P0107, P0108, P0116, P0117, P0118, P0125, P1114 or P1115 are not set.
2. The engine speed is between 1600-3000 RPM.
3. The Manifold Absolute Pressure (MAP) is less than 49 kPa.
4. The Engine Coolant Temperature (ECT) is more than 140°F (60°C).
5. The engine run time is more than 20 seconds.
6. The ignition voltage is more than 10 volts.

The PCM determines that this frequency is less than or more than the expected amount for 3 seconds or more.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Inspect the KS for proper installation. A KS that is loose or over torqued may cause either DTC to set.

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

1. 2 This step ensures the malfunction is present.
2. 3 This test will isolate the KS from the rest of the circuit.
3. 4 Tapping on the engine block will simulate an engine knock.

Scheme 417

Scheme 418

DTC P0335: CRANKSHAFT POSITION SENSOR CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The crankshaft position (CKP) sensor signal indicates the crankshaft speed and position. The CKP sensor is connected directly to the Powertrain Control Module (PCM), and consists of the following circuits

1. The 12-volt reference circuit.
2. The low reference circuit.
3. The CKP sensor signal circuit.

If the PCM detects there is no signal from the CKP sensor for 3 seconds, DTC P0335 sets.

1. DTCs P0101, P0102, P0103, P0341, P0342, or P0343 are not set.
2. The camshaft position (CMP) sensor signal is transitioning.
3. The Mass Air Flow (MAF) is more than 3 g/s in the crank mode.
4. The MAF is more than 5 g/s in the running mode.

The PCM determines there is no signal from the CKP sensor for more than 3 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The following conditions may cause this DTC to set

1. Excessive air gap between the CKP sensor and the reluctor wheel.
2. Crankshaft reluctor wheel damage or improper installation.
3. Foreign material passing between the CKP sensor and the reluctor wheel.
4. Insufficient fuel.

Excess crankshaft end play causes the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in any one of the following

1. A no-start.
2. A start and stall.
3. Erratic performance.

For an intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 3 This step determines if the fault is present.
2. 6 This step simulates a CKP sensor signal to the PCM. If the PCM receives the signal, the fuel pump will operate for about 2 seconds.

Scheme 419

Scheme 420

DTC P0336: CRANKSHAFT POSITION SENSOR CIRCUIT PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The crankshaft position (CKP) sensor signal indicates the crankshaft speed and position. The CKP sensor is connected directly to the Powertrain Control Module (PCM), and consists of the following circuits

1. The 12-volt reference circuit.
2. The low reference circuit.
3. The CKP sensor signal circuit.

If the PCM detects that the CKP sensor signal is inconsistent for 120 seconds, DTC P0336 sets.

The engine is cranking or running.

The PCM determines that the CKP sensor signal is out of range for more than 120 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The following problems may cause this DTC to set

1. Poor connections.
2. Crankshaft reluctor wheel damage or improper installation.
3. Excessive air gap between the sensor and the reluctor wheel.
4. The engine running out of fuel.
5. The crankshaft rotates backwards, this DTC sets. This condition is only with vehicles equipped with a manual transmission. This condition occurs when a vehicle is on an incline and the clutch is released and an engine stall occurs.

Excess crankshaft end play will cause the CKP sensor reluctor wheel to move out of alignment with the CKP sensor. This could result in any one of the following conditions

1. A no-start.
2. A start and stall.
3. Erratic performance.

For an intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 2 This step verifies that the malfunction is present.
2. 3 This step inspects for electromagnetic interference (EMI) on the CKP sensor circuits.

Scheme 421

Scheme 422

DTC P0341: CAMSHAFT POSITION SENSOR CIRCUIT PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The camshaft position (CMP) sensor works in conjunction with a 1 X reluctor wheel on the camshaft. The Powertrain Control Module (PCM) provides a 12-volt reference to the CMP sensor as well as a low reference and a signal circuit.

As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads.

The CMP uses this 1 X signal is used by the PCM to determine if the cylinder is at Top Dead Center (TDC) is on the firing stroke or the exhaust stroke. The PCM can determine TDC for all cylinders by using the CKP sensor 24 X signal alone. The engine will start without a CMP signal as long as the PCM receives the CKP sensor 24 X signal. A slightly longer cranking time may be a symptom of this condition. The system attempts synchronization and looks for an increase in engine speed indicating that the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes that the PCM incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. If the PCM detects that a CMP to CKP mis-match has occurred DTC P0341 sets.

The engine speed is less than 4,000 RPM.

The PCM detects that a CMP to CKP mis-match has occurred.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The following conditions may cause this DTC to set

1. Camshaft reluctor wheel damage.
2. Sensor contact with the reluctor wheel.
3. Foreign material passing between the sensor and the reluctor wheel.
4. Excessive camshaft end-play.
5. Wiring routed too close to secondary ignition components.

If the condition is intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 3 This step inspects for electromagnetic interference (EMI) on the CMP sensor circuits.
2. 6 Damage to the face of the sensor could indicate foreign material passing between the CMP sensor and the reluctor wheel. This condition would cause this DTC to set. Damage to the reluctor wheel would affect the CMP sensor output.

Scheme 423

DTC P0342: CAMSHAFT POSITION SENSOR SIGNAL LOW

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The camshaft position (CMP) sensor works in conjunction with a 1 X reluctor wheel on the camshaft. The Powertrain Control Module (PCM) provides a 12 volt reference to the CMP sensor as well as a low reference and a signal circuit.

As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads.

The CMP sensor 1 X signal is used by the PCM to determine if the cylinder at Top Dead Center (TDC) is on the firing stroke or the exhaust stroke. The PCM can determine TDC for all cylinders by using the CKP sensor 24 X signal alone. The engine will start without a CMP signal as long as the PCM receives the CKP sensor 24 X signal. A slightly longer cranking time may be a symptom of this condition. The system attempts synchronization and looks for an increase in engine speed indicating that the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes that the PCM incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. If the PCM detects that a CMP signal is constantly low, DTC P0342 sets.

The engine is running and the engine speed is less than 4000 RPM.

The PCM detects the cam signal is stuck low for 1.5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The following conditions may cause this DTC to set

1. Camshaft reluctor ring damage.
2. The sensor coming in contact with the reluctor ring.
3. Foreign material passing between the sensor and the reluctor ring.
4. Excessive camshaft end-play.
5. Wiring routed too close to secondary ignition components.

If the condition is intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 This step tests the CMP sensor signal circuit. Applying a voltage causes the CMP sensor high to low and low to high parameter to increase if the circuit and the PCM are operating properly.

Scheme 424

Scheme 425

DTC P0343: CAMSHAFT POSITION SENSOR SIGNAL HIGH

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The camshaft position (CMP) sensor works in conjunction with a 1 X reluctor wheel on the camshaft. The Powertrain Control Module (PCM) provides a 12-volt reference to the CMP sensor as well as a low reference and a signal circuit.

The CMP sensor determines whether a cylinder is on a firing stroke or on an exhaust stroke. As the camshaft rotates, the reluctor wheel interrupts a magnetic field produced by a magnet within the sensor. The sensors internal circuitry detects this and produces a signal which the PCM reads.

The CMP sensor 1 X signal is used by the PCM to determine if the cylinder at Top Dead Center (TDC) is on the firing stroke or the exhaust stroke. The PCM can determine TDC for all cylinders by using the CKP sensor 24 X signal. A slightly longer cranking time may be a symptom of this condition. The system attempts synchronization and looks for an increase in engine speed indicating that the engine started. If the PCM does not detect an increase in engine speed, the PCM assumes that the PCM incorrectly synchronized to the exhaust stroke and re-syncs to the opposite cam position. If the PCM detects that the CMP signal is constantly high, DTC P0343 sets.

The engine speed is less than 4000 RPM.

The PCM detects the CAM signal is high for 1.5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The following conditions may cause this DTC to set

1. Camshaft reluctor ring damage.
2. The sensor coming in contact with the reluctor ring.
3. Foreign material passing between the sensor and the reluctor ring.
4. Excessive camshaft end-play.
5. Wiring routed too close to secondary ignition components.

If the condition is intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 This step tests the CMP sensor signal circuit. Applying a voltage causes the CMP sensor high to low and low to high parameter to increase if the circuit and the PCM are operating properly.

Scheme 426

Scheme 427

DTC P0351-P0358: IGNITION CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The ignition system on this engine uses an individual ignition coil for each cylinder. The Powertrain Control Module (PCM) controls the ignition system operation. The PCM controls each coil using one of 8 Ignition Control (IC) circuits. The PCM commands the IC circuit low when a spark event is requested. This causes the IC module to energize the ignition coil to create a spark at the spark plug. Each ignition coil has the following circuits

1. The Ignition Control (IC) circuit.
2. The ignition 1 voltage circuit.
3. A ground circuit.
4. A reference low circuit.

The sequencing and timing are PCM controlled. This DTC sets when the IC circuit is out of range.

The engine is operating.

The PCM detects the IC circuit is grounded, open, or shorted to voltage for less than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 3 This step verifies the integrity of the IC circuit and the PCM output.
2. 4 This step tests for a short to ground on the IC circuit.

Scheme 428

Scheme 429

The Powertrain Control Module (PCM) tests the Exhaust Gas Recirculation (EGR) system during deceleration. The PCM does this by momentarily commanding the EGR valve to open while monitoring the signal circuit of the Manifold Absolute Pressure (MAP) sensor. When the EGR valve is opened, the PCM will expect to see a predetermined increase in MAP. If the expected increase in MAP is not detected, the PCM records the amount of MAP difference that was detected and adjusts a calibrated fail counter towards a calibrated fail threshold level. The number of EGR flow test counts required to exceed the fail threshold may vary according to the amount of detected EGR flow error.

Normally, the PCM will only allow one EGR flow test during an ignition cycle. TO aid in verifying a repair, the PCM will allow up to 13 EGR flow test counts during the first ignition cycle following a code clear event. Between 8-13 EGR flow test counts should be sufficient for the PCM to determine adequate EGR flow and pass the EGR flow test. If the PCM detects an EGR flow error, DTC P0401 sets.

1. DTCs P0101, P0102, P0103, P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0200, P0220, P0300, P0335, P0336, P0404, P0500, P0502, P0503, P0506, P0507, P0562, P0563, P1125, P1404, P2135 are not set.
2. The ignition 1 signal parameter is between 11-18 volts.
3. The Throttle Position (TP) sensor parameter is less than 1.2 percent.
4. The Intake Air Temperature (IAT) sensor parameter is between 32-212° F (0-100° C).
5. The Engine Coolant Temperature (ECT) sensor parameter is more than 140° F (60° C).
6. The engine speed parameter is between 725-1700 RPM.
7. The Manifold Absolute Pressure (MAP) sensor parameter is between 18-42 kPa.
8. The Mass Air Flow (MAF) sensor parameter does not change more than 3 grams per second.
9. The vehicle speed sensor parameter is more than 25 MPH during deceleration.
10. The Barometric Pressure (BARO) is more than 75 kPa.
11. The vehicle will need to be driven at more 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 EGR flow test to run. As the EGR flow test is running, you will see the Desired EGR position parameter and the EGR position sensor parameter on the scan tool momentarily change from 0 to a calibrated value above 0.

The MAP changes monitored by the PCM during the EGR flow test indicate an insufficient amount of EGR flow.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Inspect for the following conditions

1. A vacuum restriction to the MAP sensor. A skewed MAP sensor reading can cause the PCM to read incorrect MAP changes during the EGR flow test.
2. An engine that is running poorly due to a mechanical condition. These types of conditions can cause low engine vacuum and thus cause a higher than expected MAP sensor reading.
3. Excessive back pressure in the exhaust system may cause this DTC to set. This condition can cause low engine vacuum and thus cause a higher than expected MAP sensor reading, Possible causes of this could be a restriction in the exhaust system or non Original Equipment Manufacture (OEM) exhaust parts.
4. Exhaust system leaks can cause an insufficient amount of EGR flow through the EGR valve. This condition can cause less than expected changes due to insufficient exhaust back pressure. Possible causes of this could be a leaking exhaust system, a leaking EGR pipe or non Original Equipment Manufacture (OEM) exhaust parts.

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

1. 2 MAP sensor faults must be diagnosed first. A skewed MAP sensor reading could cause this DTC to set.

Scheme 430

The Powertrain Control Module (PCM) monitors the EGR position sensor parameter of the Exhaust Gas Recirculation (EGR) valve to ensure that the valve responds properly to commands from the PCM. The PCM compares the EGR position sensor parameter with the desired EGR position parameter when the valve is commanded open. If the PCM detects a difference of 12 percent between the EGR position sensor parameter and desired EGR position parameter for a calibrated amount of time, DTC P0404 will set.

1. The ignition 1 signal parameter is between 11-18 volts.
2. The EGR valve is commanded open.

1. The difference between the desired EGR position parameter and the EGR position sensor parameter is more than 12 percent.
2. The condition is present for more than 10 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

1. Inspect for excessive deposits on the EGR pintle or seat. Remove EGR valve.
2. Inspect for deposits that may interfere with the EGR valve pintle extending completely or may cause the pintle to stick.
3. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 431

Scheme 432

Scheme 433

The Exhaust Gas Recirculation (EGR) valve position sensor is monitored by the Powertrain Control Module (PCM). The 5-volt reference circuit, low reference circuit and the EGR valve position signal circuit are used by the PCM to determine the EGR valve position. If the EGR valve position sensor signal voltage is pulled below a calibrated value, DTC P0405 sets.

The Ignition 1 Signal parameter is between 11-18 volts.

1. The EGR Position Sensor parameter is less than 0.16 volts.
2. The above condition is met for more than 5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Scheme 434

Scheme 435

DTC P0420: : TWC SYSTEM - LOW EFFICIENCY - BANK 1 & DTC P0430: TWC SYSTEM - LOW EFFICIENCY - BANK 2

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The engine systems uses a 3-way catalytic converter (TWC) to control emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides Of Nitrogen (NOx). The catalyst within the TWC promotes a chemical reaction, which oxidizes the HC and CO that are present in the exhaust system. This reaction converts these chemicals into harmless water vapor and carbon dioxide. The catalyst also reduces the NOx which converts into nitrogen. The Powertrain Control Module (PCM) monitors this process using Heated Oxygen Sensors (HO2S) bank 1 sensor 2 and HO2S bank 2 sensor 2, which are located in the exhaust stream past the TWC. These sensors are referred to as catalyst monitor sensors. The catalyst monitor sensors produce an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalysts ability to effectively convert the exhaust emissions. If the catalyst is functioning correctly, the catalyst monitor signals will be far less active than that of the signals which are produced by the fuel control HO2S 1 bank 1 and fuel control HO2S bank 2. This indicates that the TWC oxygen storage capacity is at an acceptable threshold. When the response time of the catalyst monitors are close to that of the fuel control sensors, the ability of the catalyst to store oxygen is considered to be below an acceptable threshold. If the PCM detects this condition, DTC P0420 catalyst low efficiency for bank 1 or DTC P0430 catalyst low efficiency for bank 2 sets.

1. DTCs P0101-P0103, P0106-P0108, P0112, P0113, P0117, P0118, P0120, P0125, P0128, P0131-P0135, P0137, P0138, P0140, P0141, P0151-P0155, P0157, P0158, P0160, P0161, P0171, P0172, P0174, P0175, P0200, P0220, P0300, P0325, P0327, P0332, P0335, P0336, P0341-P0343, P0351-P0358, P0442, P0443, P0446, P0452, P0453, P455, P0496, P0502, P0503, P1125, P1133, P1153, P1514, P1516, P1518, P2108 or P2135 are not set.
2. The Intake Air Temperature (IAT) is 19-185°F (-7-85°C).
3. The Barometric (BARO) pressure is more than 74 kPa.
4. The vehicle has been driven at more than 900 RPM for 50 seconds.
5. The Engine Coolant Temperature (ECT) is 158-248°F (70-120°C).
6. The engine must be at idle for one of the following amounts of time: 45 seconds in neutral for manual transmissions. 40 seconds in gear for automatic transmissions.
7. The Closed Loop fuel control is enabled.

The PCM determines the oxygen storage capability of the catalytic converter has degraded below a calibrated threshold.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) the first time the diagnostic runs and fails.
2. The control module will set the DTC and records the operating conditions at the time the diagnostic fails. The control module stores the failure information in the scan tools Freeze Frame/Failure Records.

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

1. The catalyst test may abort due to a change in the engine load. DO NOT change the engine load during the test. During the test, DO NOT reset the AC, Coolant Fan, or the Heater Motor.
2. Inspect the fuel control oxygen sensor wiring harness for a short to the catalysts monitor wiring harness.
3. Driving the vehicle under the conditions outlined in «DRIVE CYCLES»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__drive-cycles) can verify whether the fault is present.
4. Certain conditions may cause a catalytic converter to degrade. These conditions may include the following: An engine misfire, which can cause catalytic convertor overheating. High engine oil high coolant consumption. Retarded spark timing. A conditions that may cause low secondary ignition voltage, which can cause incomplete combustion. A lean fuel mixture. A rich fuel mixture. A shorted oxygen sensor wiring harness.
5. Correct any condition that may cause an engine performance concern.
6. If an intermittent condition cannot be duplicated, the information included in the Freeze Frame/Failure Records can be useful in determining the vehicle operating conditions when the DTC was set.

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

1. 6 This step inspects for conditions than can cause the 3-way catalytic converter efficiency to appear degraded.
2. 8 A catalytic converter which has been discolored may be due to an engine running rich, lean or had a previous severe misfire. Verifying the fuel trim percentages may be of assistance in determining if such a condition exists.

Scheme 436

Scheme 437

DTC P0442: EVAP SYSTEM - SMALL LEAK

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

This diagnostic tests the Evaporative Emission (EVAP) system for a small leak when the key is turned OFF and the correct conditions are met.

Heat is transferred into a vehicle fuel tank while the vehicle is operating. When the vehicle is turned OFF, a change in the fuel tank vapor temperature occurs, which may result in corresponding pressure changes in the fuel vapor space. This change is monitored by the control module using the fuel tank pressure sensor input. The control module then makes a judgement on the integrity of the system. With a 0.020 inch (0.51 mm) leak in the system, the amount of pressure change observed is significantly less than that of a sealed system.

If the control module detects a pressure change less than a calibrated amount, DTC P0442 sets.

1. DTCs P0100, P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0335, P0336, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P0500, P0502, P0721, P0722, P1106, P1107, or P1683 are not set.
2. The diagnostic runs once with a 10 hour minimum between tests after a fail.
3. DTC P0455 must run and pass.
4. The start up intake air temperature (IAT) is between 39-86° F (4-30° C).
5. The start up Engine Coolant Temperature (ECT) is less than 86° F (30° C).
6. The start up IAT and ECT are within 15° F (8° C).
7. The Barometric Pressure (BARO) is more than 74 kPa.
8. The ambient air temperature is between 36-90° F (2-32° C).
9. The engine run time minimum is 600 seconds.
10. The odometer displays more than 10 miles.
11. The vehicle has traveled more than 3 miles this trip.
12. The ECT is more than 158° F (70° C).
13. The fuel level is between 15-85 percent.
14. The ignition is OFF.

The control module detects a pressure change that is less than a calibrated amount.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. 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.

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

1. To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light.
2. To improve visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT.
3. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 3 Introducing smoke in 15 second intervals may allow smaller leak areas to be more noticeable. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. 5 This step verifies that repairs are complete and that no other condition is present.

Scheme 438

Scheme 439

DTC P0443: EVAP PURGE SOLENOID CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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

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

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

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 This step tests if the concern is active. The EVAP purge valve is PWM. You should hear a clicking sound when the purge valve is commanded to 50 percent. The clicking sound should stop when the EVAP purge valve is commanded to 0 percent. The rate at which the valve cycles should increase when the commanded state is increased, and decrease when the commanded state is decreased. Repeat the commands as necessary.
2. 5 This step verifies that the control module is providing ground to the EVAP purge valve.
3. 6 This step tests if a ground is constantly being applied to the EVAP purge valve.

Scheme 440

Scheme 441

DTC P0446: EVAP VENT VALVE PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

This DTC tests the Evaporative Emission (EVAP) system for a restricted or blocked EVAP vent path. The control module commands the EVAP canister purge solenoid ON and the EVAP canister vent solenoid ON. This allows vacuum to be applied to the EVAP system. Once a calibrated vacuum level has been reached, the control module commands the EVAP canister purge solenoid OFF and the EVAP canister vent solenoid 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 inches H2O in a calibrated time, this DTC sets.

1. DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0500, P1111, P1112, P1114, or P1115 are not set.
2. The ignition voltage is between 10-18 volts.
3. The Barometric (BARO) pressure is more than 75 kPa.
4. The fuel level is between 15-85 percent.
5. The Engine Coolant Temperature (ECT) is between 39-86°F (4-30°C).
6. The Intake Air Temperature (IAT) is between 39-86°F (4-30°C).
7. The start up ECT and IAT are within 16°F (9°C) of each other.

1. The Fuel Tank Pressure (FTP) is less than -10 in. H2O.
2. The condition is present for more than 30 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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. If the condition is intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 3 This test determines if the failure is present or intermittent.

Scheme 442

Scheme 443

DTC P0449: EVAP VENT VALVE PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

An ignition voltage is supplied to the Evaporative Emission (EVAP) canister vent valve. The control module grounds the EVAP canister vent valve control circuit to close the valve be means of an internal switch called a driver. The scan tool displays the commended state of the EVAP canister vent valve as ON or OFF. The control module monitors the status of the driver. If the control module detects an incorrect voltage for the commanded state of the driver, this DTC sets.

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

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

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 A click should be heard or felt when the valve operates. Ensure that both the ON and the OFF states are commanded. Repeat the commands as necessary.
2. 5 This step verifies that the control module is providing ground to the EVAP vent valve.
3. 6 This step tests if the EVAP vent valve control circuit is grounded.

Scheme 444

Scheme 445

DTC P0452: FUEL TANK PRESSURE SENSOR - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

The Fuel Tank Pressure (FTP) sensor measures the difference between the air pressure or vacuum in the evaporative emission (EVAP) system, and the outside pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage goes below a calibrated value, this DTC sets.

If FTP sensor signal voltage is 1.5 volts or more the FTP has negative pressure/vacuum. If the FTP sensor signal voltage is 1.5 volts or less the FTP has positive pressure.

The engine is running.

1. The fuel tank pressure sensor voltage is less than 0.1 volt.
2. All conditions are present for greater than 5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The number below refers to the step number in the diagnostic procedure.

1. 5 This step tests for the proper operation of the circuit in the high voltage range.
2. 6 The 5-volt reference circuit for the FTP sensor is routed through connector C152. This area may provide a good test point for diagnosing concerns with this circuit.
3. 7 The FTP sensor signal circuit is routed through connector C152. This area may provide a good test point for diagnosing concerns with this circuit.

Scheme 446

Scheme 447

DTC P0453: FUEL TANK PRESSURE SENSOR - HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

The Fuel Tank Pressure measures the difference between the air pressure or vacuum in the Evaporative Emission (EVAP) system, and the outside air pressure. The control module supplies a 5-volt reference and a low reference circuit to the FTP sensor. The FTP sensor signal circuit voltage varies depending on EVAP system pressure or vacuum. If the FTP sensor signal voltage increases above a calibrated value, this DTC sets.

If FTP sensor signal voltage is 1.5 volts or more the FTP has negative pressure/vacuum. If the FTP sensor signal voltage is 1.5 volts or less the FTP has positive pressure.

The engine is running.

1. The fuel tank pressure sensor voltage is more than 4.9 volts.
2. All conditions are present for greater than 5 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The number below refers to the step number in the diagnostic procedure.

1. 2 If DTC P0641 or P0651 is set, the 5-volt reference circuit maybe shorted to a voltage.

Scheme 448

Scheme 449

DTC P0455: EVAP SYSTEM LEAK DETECTED - GROSS LEAK/NO FLOW

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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.

1. DTC P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0500, P1111, P1112, P1114, or P1115 are not set.
2. The engine is running.
3. The ignition voltage is between 10-18 volts.
4. The Barometric Pressure (BARO) is more than 75 kPa.
5. The fuel level is between 15-85 percent.
6. The Engine Coolant Temperature (ECT) is between 39-149° F (4-65° C).
7. The Intake Air Temperature (IAT) is between 39-167° F (4-75° C).
8. The start-up ECT and IAT are within 16° F (9° C) of each other.

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

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The fires 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.

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

1. To help locate intermittent leaks, use the J 41413-200 Evaporative Emissions System Tester (EEST) to introduce smoke into the EVAP system. Move all EVAP components while observing smoke with the J 41413-SPT High Intensity White Light. Introducing smoke in 15 second intervals will allow less pressure into the EVAP system. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. A temporary blockage in the EVAP purge solenoid purge pipe or EVAP canister could cause an intermittent condition. Inspect and repair intermittent condition. Inspect and repair any restriction in the EVAP system.
3. To improve visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with the J 41413-SPT.
4. 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.
5. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The number below refers to the step number in the diagnostic procedure.

1. 3 Introducing smoke in 15 second intervals may allow smaller leak areas to be more noticeable. When the system is less pressurized, the smoke will sometimes escape in a more condensed manner.
2. 5 This step verifies proper operation of the Fuel Tank Pressure (FTP) sensor.
3. 6 A normal operating FTP sensor should increase above 5 inches of H2O and stop between 6 and 7 inches of H2O.

Scheme 450

Scheme 451

Scheme 452

DTC P0496: EVAP SYSTEM HIGH PURGE FLOW

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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 time, this DTC sets.

If the control module command is ON the EVAP purge valve is OPEN and the EVAP canister vent valve is CLOSED. If the control module command is OFF the EVAP purge valve is CLOSED and the EVAP canister vent valve is OPEN.

1. DTC P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0220, P0442, P0443, P0446, P0449, P0452, P0453, P0455, P0500, P1111, P1112, P1114, or P1115 are not set.
2. The ignition voltage is between 10-18 volts.
3. The Barometric Pressure (BARO) is more than 75 kPa.
4. The fuel level is between 15-85 percent.
5. The Engine Coolant Temperature (ECT) is between 39-86° F (4-30° C).
6. The Intake Air Temperature (IAT) is between 39-86° F (4-30° C).
7. The start-up ECT and IAT are within 16° F (9° C) of each other.

1. A continuous open purge flow condition is detected during the diagnostic test.
2. The fuel tank pressure decreases to less than -11 inches H2O.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic 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.

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

Scheme 453

DTC P0506: IDLE CONTROL SYSTEM - RPM LOW & DTC P0507: IDLE CONTROL SYSTEM - RPM HIGH

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Throttle Actuator Control (TAC) system uses vehicle electronics and components to calculate and control the position of the throttle plate. In order to decrease idle speed the TAC system closes the throttle plate reducing airflow into the engine. In order to increase idle speed the TAC system opens the throttle plate allowing more airflow into the engine. If the actual idle RPM does not match the desired idle RPM within a calibrated time, this DTC set.

1. DTCs P0107, P0108, P0112, P0113, P0117, P0118, P0120, P0125, P0171, P0172, P0200, P0220, P0300, P0442, P0446, P0452, P0453, P0641, P0651, P1514, P1515, P1516 or P2135 are not set.
2. The engine is operating for at least 2 seconds.
3. The Engine Coolant Temperature (ECT) is greater than -40°F (-40°C).
4. The Intake Air Temperature (IAT) is greater than -40°F (-40°C).
5. The Barometric (BARO) pressure is greater than 65 kPa.
6. The system voltage is between 9-18 volts.
7. The vehicle speed is less than 3 MPH.

1. The actual idle speed is 100 RPM less than or 100 RPM more than the desired idle speed.
2. All of the above conditions are present for 15 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

The number below refers to the step number in the diagnostic procedure.

1. 2 This test determines if the engine can achieve the commanded RPM. If the engine does not reach the commanded RPM, the test determines whether the RPM is too high or too low.

Scheme 454

DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681, P1683 & P2610: PCM MEMORY

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

This diagnostic applies to internal microprocessor integrity conditions within the Powertrain Control Module (PCM). This diagnostic also addresses if the PCM is not programmed.

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

1. 2 A DTC P0602 indicates the PCM is not programmed.

Scheme 455

The Powertrain Control Module (PCM) provides 5 volts to the following sensors

1. The Engine Oil Pressure (EOP) sensor.
2. The Exhaust Gas Recirculation (EGR) valve.
3. The Manifold Absolute Pressure (MAP) sensor.

These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The PCM monitors the voltage on the 5-volt reference circuit. If the PCM detects that the voltage is out of tolerance, DTC P0641 sets.

The engine is running.

1. The PCM detects a voltage out of tolerance condition on the 5-volt reference circuit.
2. The above condition is present for longer than 2 seconds.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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 condition to the Freeze Frame and updates the Failure Records.

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

Scheme 456

Scheme 457

DTC P0650: MALFUNCTION INDICATOR LAMP CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Malfunction Indicator Lamp (MIL) is located on the Instrument Panel Cluster (IPC). The MIL informs the driver than an emission system fault has occurred and that the engine control system requires service. The control module monitors the MIL control circuit for conditions that are incorrect for the commanded state of the MIL. For example, a failure condition exists if the control module detects low voltage when the MIL is commanded OFF, or high voltage when the MIL is commanded ON. If the control module detects an improper voltage on the MIL control circuit, DTC P0650 will set.

The engine is running.

1. The control module detects that the commanded start of the MIL driver and the actual state of the control circuit do not match.
2. The conditions are present for a minimum of 30 seconds.

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.

1. A Last Test Failed, or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

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

1. 4 This step tests for a short to ground in the MIL control circuit. With the Powertrain Control Module (PCM) disconnected and the ignition ON, the MIL should be OFF.
2. 5 This step tests for a short to voltage on the MIL control circuit. With the fuse removed, there should be no voltage on the MIL control circuit.

Scheme 458

Scheme 459

The Powertrain Control Module (PCM) provides 5 volts to the following sensors

1. The Air Conditioning (A/C) pressure sensor.
2. The Fuel Tank Pressure (FTP) sensor, if equipped.

These 5-volt reference circuits are independent of each other outside the PCM, but are bussed together inside the PCM. Therefore a circuit condition on one sensor 5-volt reference circuit may affect the other sensor 5-volt reference circuits. The PCM monitors the voltage on the 5-volt reference circuit. The PCM detects that the voltage is out of tolerance, DTC P0651 sets.

The engine is running.

1. The PCM detects a voltage out of tolerance condition on the 5-volt reference circuit.
2. The above conditions is present for longer than 2 seconds.

Action Take When DTC Sets

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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 to the Freeze Frame and updates the Failure Records.

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

Scheme 460

Scheme 461

The Malfunction Indicator Lamp (MIL) requests circuit signals the Engine Control Module (ECM) that the Transmission Control Module (TCM) is requesting MIL illumination.

The engine is running.

The TCM is requesting MIL illumination, or that the MIL request circuit is shorted to ground.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. 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.

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

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

1. 2 If the TCM has DTCs set that are requesting MIL illumination, those DTCs must be diagnosed first.

Scheme 462

The Transmission Control Module (TCM) Malfunction Indicator Lamp (MIL) request circuit signals the Powertrain Control Module (PCM) that the TCM is requesting MIL illumination.

The ignition is ON.

The PCM is detecting an incorrect voltage level on the TCM request circuit.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

1. The control module turns OFF the Malfunctions Indicator Lamp (MIL) after 3 consecutive ignition cycles that the diagnostic runs and does not fail.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. A history DTC clears after 40 consecutive warm-up cycles, if not failures are reported by this or any other emission related diagnostic.
4. Clear the MIL and the DTC with a scan tool.

Scheme 463

Scheme 464

The Manifold Absolute Pressure (MAP) sensor responds to pressure changes in the intake manifold. The pressure changes occur based on changes in the intake manifold. The pressure changes occur based on the engine load. The MAP sensor has the following circuits

1. 5-volt circuit.
2. Low reference circuit.
3. MAP 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 the PCM detects a MAP sensor signal voltage that is intermittently high, DTC P1106 sets.

1. DTC P0120, P0220, P1125, P1514, P1515, P1516, P1518, P2108, P2120, P2121, P2125, P2126, P2130, P2131, P2135 are not set.
2. 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 4 minutes at less than -22° F (-30° C) to 30 seconds at more than 85° F (30° C).
3. The throttle angle is less than 1 percent when the engine speed is less than 1200 RPM.
4. The throttle angle is less than 20 percent when the engine speed is more than 1200 RPM.

The PCM detects that the MAP sensor voltage is more than 4.9 volts.

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

Conditions For Clearing DTC

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

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

1. 3 This step attempts to pinpoint the location of the intermittent fault.

Scheme 465

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

1. 5-volt reference circuit.
2. Low reference circuit.
3. MAP 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 the PCM detects a MAP sensor signal voltage that is intermittently low, DTC P1107 sets.

1. DTC P0120, P0220, P1125, P1514, P1515, P1516, P1518, P2108, P2120, P2121, P2125, P2126, P2130, P2131, or P2135 are not set.
2. The engine is running.
3. The throttle angle is 0 percent when the engine speed is less than 800 RPM.
4. The throttle angle is more than 12.5 percent when engine speed is more than 800 RPM.

The PCM detects that the MAP sensor voltage is less than 0.1 volt.

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

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

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

1. 3 This step attempts to pinpoint the location of the intermittent t fault.

Scheme 466

DTC P1111: INTAKE AIR TEMPERATURE SENSOR CIRCUIT - INTERMITTENT HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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.

1. DTCs P0101, P0102, P0103, or P0113 are not set.
2. The engine run time is more than 120 seconds.
3. The engine coolant temperature is more than 140°F (60°C).
4. The vehicle speed is less than 7 MPH.
5. The mass air flow is less than 15 g/s.

The intake air temperature is less than -36°F (-38°C) for a calibrated amount of time.

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

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

1. An IAT sensor or PCM which is intermittently shorted, open, or skewed is possible, yet very unlikely.
2. A skewed sensor could result in poor driveability conditions.
3. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 467

DTC P1112: INTAKE AIR TEMPERATURE SENSOR CIRCUIT - INTERMITTENT LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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.

1. DTCs P0112, P0500, P0502, and P0503 are not set.
2. The engine run time is more than 45 seconds.
3. The vehicle speed is more than 25 MPH.
4. The ECT sensor parameter is less than 257° F (125° C).

The PCM detects that the IAT sensor parameter is more than 252° F (128° C) intermittently for a calibrated amount of time.

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

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

1. An IAT sensor or PCM which is intermittently shorted, open, or skewed is possible, yet very unlikely.
2. A skewed sensor could result in poor driveability complaints.
3. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 468

DTC P1114: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT - INTERMITTENT LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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, this Diagnostic Trouble Code (DTC) will set.

Engine run time is more than 10 seconds.

The PCM detects that the ECT sensor parameter is more than 282° F (139° C) intermittently for a calibrated amount of time.

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

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

1. An ECT sensor or PCM which is intermittently shorted, open, or skewed is possible, yet very unlikely.
2. An intermittent short to ground in the ECT sensor signal circuit could result in a DTC P1114.
3. Use the Temperature vs Resistance Value scale 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. See «TEMPERATURE VS. RESISTANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 469

DTC P1115: ENGINE COOLANT TEMPERATURE SENSOR CIRCUIT - INTERMITTENT HIGH VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnostic testing requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS article.

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, this Diagnostic Trouble Code (DTC) will set.

Engine run time is more than 60 seconds.

The PCM detects an ECT of less than -36°F (-38°C), as measured by the ECT sensor for a calibrated amount of time.

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

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

1. An ECT sensor or PCM which is intermittently shorted, open, or skewed is possible, yet very unlikely.
2. An intermittent open or short to voltage in the ECT sensor signal circuit could result in a DTC P1115.
3. Use the Temperature vs Resistance Value scale 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. See «TEMPERATURE VS. RESISTANCE»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l) .
4. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 470

DTC P1125: ACCELERATOR PEDAL POSITION SENSORS OUT OF RANGE OR DISAGREE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Accelerator Pedal Position (APP) sensor is mounted on the accelerator pedal assembly. The sensor is actually 2 individual APP sensors within 1 housing. Two separate signal circuits are used in order to connect the accelerator pedal sensor assembly, and the Throttle Actuator Control (TAC) module

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

If only 1 APP sensor DTC is set, the redundant APP systems allow the TAC system to continue operating normally. This DTC sets if the Powertrain Control Module (PCM) detects a condition with more than 1 APP sensor. One APP sensor DTC will not cause the Reduced Engine Power message to be displayed. 2 APP sensor DTCs for the same sensor also will not cause the Reduced Engine Power message to be displayed. However, if two or more DTCs are set involving more than 1 APP sensor, this DTC will set and the Reduced Engine Power message is displayed.

1. DTCs P1517 or P1518 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is greater than 5.23 volts.

1. Two or more APP sensors are out of range or 2 APP sensors disagree.
2. All of the above conditions present for less than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode; or, under certain conditions the control module commands the engine OFF.
4. The message center displays Reduced Engine Power.

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

1. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. The APP sensor 1 and the Throttle Position (TP) sensor 1, 5-volt reference circuits are internally connected within the TAC module.
3. The APP sensor 2 and the TP sensor 2, 5-volt reference circuits are internally connected within the TAC module.
4. When the TAC module detects a condition within the TAC system more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Remember this if you review the information stored in Captured Info.
5. If an intermittent condition is suspected, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 2 When the problems are corrected which are causing the APP sensor DTCs to set, the status of this DTC will change to history.

Scheme 471

DTC P1133: HO2S CIRCUIT - INSUFFICIENT SWITCHING - BANK 1, SENSOR 1 & DTC P1153: HO2S CIRCUIT - INSUFFICIENT SWITCHING - BANK 2, SENSOR 1

Note. For HO2S identification (Scheme 381)

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Heated Oxygen Sensors (HO2S) are used for fuel control and post catalyst monitoring. Each HO2S compared the oxygen content of the surrounding air with the oxygen content in the exhaust stream. The HO2S must reach operating temperature to provide an accurate voltage signal. Heating elements inside the HO2S minimize the time required for the sensors to reach operating temperature. The Powertrain Control Module (PCM) supplies the HO2S with a reference, or bias, voltage of about 450 mV. When the engine is first started the PCM operates in open loop, ignoring the HO2S voltage signal. Once the HO2S reaches operating temperature and closed loop is achieved, the HO2S generates a voltage within a range of 0-1000 mV that fluctuates above and below bias voltage. High HO2S voltage indicates a rich exhaust stream; low HO2S voltage indicates a lean exhaust stream. This diagnostic will only run once per ignition cycle. The PCM monitors the number or rich-to-lean and lean-to-rich transitions. A transition is defined as, the HO2S voltage changes from above 600 mV to below 250 mV or from below 250 mV to above 600 mV. If the PCM detects that the number or transitions were less than a specified value, DTCs P1133 or P1153 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0200, P0220, P0300, P0401, P0404, P0405, P0442, P0446, P0452, P0453, P0455, P0496, P1125, P1258, P1404, P1514, P1515, P1516, P1518, P2108, or P2135 are not set.
2. The Engine Coolant Temperature (ECT) sensor is more than 140°F (60°C).
3. The engine run time is more than 160 seconds.
4. The Evaporative (EVAP) emissions purge solenoid command is more than 1 percent.
5. The Mass Airflow (MAF) sensor is between 29-55 g/s.
6. The engine speed is between 1000-3000 RPM.
7. For vehicles with TAC, the TP indicated angle is 5 percent more than the value observed at idle.
8. The loop status is Closed.
9. The ignition 1 signal voltage is between 10-18 volts.
10. The fuel tank level remaining is more than 10 percent.
11. The above conditions are met for 100 seconds.

The PCM detects that the affected HO2S lean-to-rich or rich-to-lean transitions are less than a calibrated value.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

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

1. 2 If the voltage is varying above and below the specified value, the condition is not present.

Scheme 472

Scheme 473

DTC P1172: SECONDARY FUEL PUMP TRANSFER MALFUNCTION

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The secondary fuel pump is located in the rear fuel tank. The secondary fuel pump is powered by a secondary fuel pump relay. Fuel is transferred from the rear fuel tank to the front fuel tank in order to ensure all of the usable fuel volume is available to the primary fuel pump. The secondary fuel pump relay supply voltage is received from the primary fuel pump relay when the primary fuel pump is energized. The Diagnostic Trouble Code (DTC) sets when the Powertrain Control Module (PCM) commands the secondary fuel pump ON and a predetermined change in both the front and rear fuel level sensors does not occur.

1. DTCs P0461, P0462, P0463, P2066, P2067, or P2068 are not set.
2. The engine is not running.
3. The vehicle speed is 0 MPH.
4. The primary fuel level is less than 6.6 gal. (25 L).
5. The secondary fuel level is more than 0.7-2.6 gal. (3-10 L).
6. The above conditions are met for 20 seconds before the secondary pump is commanded ON.
7. The secondary fuel pump is commanded ON for 120 seconds.

The PCM does not detect a change of 1.06 gal. (4 L) in both the primary and secondary fuel level sensors with the secondary pump commanded ON for 120 seconds.

1. The PCM stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Lamp (MIL) will not illuminate.
3. The PCM records the operating conditions at the time the diagnostic fails. The PCM stores this information in the Failure Records.

1. A last test failed, or current DTC, clears when the diagnostic runs and does not fail.
2. A history DTC will clear after 40 consecutive warm-up cycles, if no failures are reported by this or any other non-emission related diagnostic.
3. Use a scan tool in order to clear the DTC.

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

1. 2 This step tests the supply voltage circuit of the secondary fuel pump relay.
2. 4 This step verifies the secondary fuel pump operation. Listen for an audible sound as the secondary fuel pump relay harness connector is jumpered.
3. 5 This step verifies that there is adequate fuel in the rear fuel tank. The rear fuel tank sensor voltage must be above 1 volt in order to continue.
4. 7 This step tests the secondary fuel pumps ability to transfer fuel. The rear fuel level sensor voltage should decrease while the secondary fuel pump is ON.
5. 8 This step tests for a short to ground on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to ground is indicated.
6. 9 This step tests for a short to voltage on the control circuit of the secondary fuel pump relay. If the test lamp illuminates, a short to voltage is indicated.
7. 10 This step verifies the secondary fuel pump relay operation. An audible click should be heard as the secondary fuel pump relay control circuit is grounded. The secondary fuel pump should turn ON as the fuel pump relay control circuit is grounded.

Scheme 474

Scheme 475

Scheme 476

Scheme 477

DTC P1258

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The PCM uses the ECT sensor to monitor the engine for an over temperature condition. This condition occurs when the coolant temperature is above 270°F (132°C). When an over temperature condition is present, DTC P1258 will set. The PCM will disable two groups of four cylinders by turning OFF the fuel injectors. By switching between the two groups of cylinders, the PCM is able to reduce the temperature of the coolant.

1. DTCs P0117, P0118, P1114, and P1115 are not active.
2. The engine is running.

The engine coolant temperature is above 132°C (270°F) for 10 seconds or more.

1. The PCM will illuminate the Malfunction Indicator Lamp (MIL) during the first trip in which the diagnostic test has been run and failed.
2. The PCM will signal the IPC to turn ON the Service Engine Soon indicator.
3. The PCM will alternately disable two groups of four cylinders by turning OFF the fuel injectors.
4. The PCM will store conditions which were present when the DTC set as Freeze Frame and File Records data.

1. The PCM will turn the MIL OFF after 3 consecutive trips that the diagnostic has been run and passed.
2. The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.
3. The DTC can be cleared by using the scan tool Clear DTC Information function.

Scheme 478

DTC P1380: EBCM DTC DETECTED ROUGH ROAD DATA UNSTABLE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) detects engine misfire events by monitoring variations in crankshaft rotation speed. Wheel speed changes caused by rough road conditions can cause changes in crankshaft speed. By monitoring the wheel speed sensors, the Anti-Lock Brake System (ABS) can determine if the vehicle is operating on a rough road. If the ABS is detecting a rough road condition severe enough to effect misfire detection, a rough road signal is sent to the PCM on the serial data circuit. If DTC P0300 is set and the rough road information is not available due to an ABS malfunction, DTC P1380 will set.

1. DTCs P0101, P0102, P0103, P0120, P0335, P0336, or P0742 are not set.
2. The vehicle speed is more than 10 MPH.
3. The engine load is less than 60 percent.
4. The engine misfire is detected and DTC P0300 set.
5. The engine speed is less than 3200 RPM.

An ABS malfunction exists preventing the PCM from receiving rough road detection data.

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

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

Scheme 479

DTC P1381: MISFIRE DETECTED - NO EBCM/PCM SERIAL DATA

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) detects engine misfire events by monitoring variations in the crankshaft rotation speed. Wheel speed changes caused by rough road conditions can cause changes in crankshaft speed. By monitoring the wheel speed sensors, the Anti-Lock Brake System (ABS) can determine if the vehicle is operating on a rough road. If the ABS is detecting a rough road condition severe enough to effect misfire detection, a rough road signal is sent to the PCM on the serial data circuit. If DTC P0300 is set and the rough road information is not available due to and ABS malfunction, DTC P1381 will set.

1. The engine load is less than 60 percent.
2. The engine speed is less than 3200 RPM.
3. The vehicle speed is more than 10 MPH.
4. Engine misfire is detected and DTC P0300 is set.

1. A serial data malfunction exists preventing the PCM from receiving rough road detection data.
2. The above conditions are met for 20 seconds.

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

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

The number below refers to the step number in the diagnostic procedure.

1. 1 This step will diagnose a malfunction in the serial data circuits.

Scheme 480

DTC P1404: EGR VALVE CLOSED PINTLE POSITION

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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. 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.

1. The ignition 1 signed parameter is between 11-18 volts.
2. The PCM has enabled the EGR valve.
3. The above conditions are met 3 times.

1. EGR position sensor is 0.29 volts more than the EGR learned minimum position when the desired EGR position is commanded to 0 percent.
2. The vehicle must be driven.
3. The condition has to be present 3 times.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
2. 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.

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

Inspect for excessive deposits on the EGR valve pintle or seat. Remove the EGR valve and check for deposits that may interfere with the EGR valve pintle extending completely or cause the pintle to stick.

If DTC is determined to be intermittent, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 2 This step verifies that the malfunction is present.

Scheme 481

Scheme 482

DTC P1514: AIRFLOW RATE EXCESSIVE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) uses the following readings in order to calculate the predicted Mass Air Flow (MAF) rate

1. The Throttle Position (TP).
2. The Barometric (BARO) pressure.
3. The Intake Air Temperature (IAT).
4. The engine RPM.

The PCM compares the predicted MAF value to the actual MAF value, and to the speed density calculation in order to verify the proper throttle operation.

1. DTCs P0601, P0602, P0604, P0606, P1515, P1516, P1517, or P1518 are not set.
2. The following DTCs are not active at the same time: P0120, P0220 and P2135.
3. The following DTCs are not active at the same time: P0120 and P0220.
4. The engine operates longer than 1 second.
5. The engine speed is greater than 500 RPM.

1. The PCM detects that the difference between the actual airflow (MAF) and the Speed Density calculated air flow is greater than expected.
2. All of the above conditions met for less than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode; or, under certain conditions the control module commands the engine OFF.
4. The message center displays Reduced Engine Power.

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

1. Inspect the throttle blade for being broken, bent, or missing.
2. Inspect the Throttle Position (TP) sensor for proper installation. A sensor that is mis-aligned could set this DTC.
3. Inspect the Throttle Actuator Control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
4. Physically and visually inspect the throttle body assembly and correct any problems that you observe. Manually move the throttle blade from closed to Wide Open Throttle (WOT). You should not need to use excess force. The throttle blade should move smoothly through the full range and then should independently return to a slightly open position.
5. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
6. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

The number below refers to the step number in the diagnostic procedure.

1. 5 Locating and repairing an individual condition may correct more than 1 DTC.

Scheme 483

DTC P1515: PREDICTED VS ACTUAL THROTTLE POSITION CORRELATION ERROR

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The commanded Throttle Position (TP), based on Accelerator Pedal Position (APP) and possibly other limiting factors, is compared to the actual TP. The 2 values should be within a calibrated range of each other. Both the Powertrain Control Module (PCM) and the Throttle Actuator Control (TAC) module redundantly monitor the commanded and actual TP. This DTC sets if the PCM detects an out-of-range condition between commanded and actual pedal position.

1. DTCs P0601, P0602, P0604, P0606, P1516, P1518 or P2108 are not set.
2. The following DTCs are not active at the same time: P0120, P0220 and P2135.
3. The following DTCs are not active at the same time: P0120 and P0220.
4. The ignition switch is in the crank or run position.
5. The ignition voltage is greater than 8.5 volts.
6. The TAC system is not in the battery saver mode.

1. The PCM detects that the commanded and actual throttle positions are not within a calibrated range of each other.
2. All above conditions met for less than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode; or, under certain conditions the control module commands the engine OFF.
4. The message center displays Reduced Engine Power.

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

1. Inspect for mechanical concerns or binding that may be temperature related. Components may not move freely in extreme heat or cold due to the presence of contaminants or ice formation.
2. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
3. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
4. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 If the TP indicated angle does not follow the movement of the throttle blade, and no TP sensor DTCs are set, there is a mechanical condition with the throttle shaft or the TP sensor.
2. 16 Locating and repairing an individual condition may correct more than 1 DTC.

Scheme 484

Scheme 485

DTC P1516: PREDICTED VS ACTUAL THROTTLE POSITION CORRELATION ERROR

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The predicted Throttle Position (TP), based on Accelerator Pedal Position (APP) and other limiting factors, is compared to the Actual throttle position. The 2 values should be within a calibrated range of each other. Both the Powertrain Control Module (PCM) and the Throttle Actuator Control (TAC) module redundantly monitor the predicted and actual throttle position. This DTC sets if the PCM detects an out of range condition between the predicted and actual throttle position.

1. DTC P1518 is not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is greater than 5.23 volts.
4. The TAC system is not in the battery saver mode.

1. The TAC module detects that the predicted and actual throttle positions are not within a calibrated range of each other or the PCM and the TAC cannot determine throttle position or both TP sensors are invalid.
2. All of the above conditions met for less than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode; or, under certain conditions the control module commands the engine OFF.
4. The message center displays Reduced Engine Power.

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

1. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set.
3. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
4. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 7 If the TP indicated angle does not follow the movement of the throttle blade, and no TP sensor DTCs are set, there is a mechanical condition with the throttle shaft or the TP sensor.
2. 18 Locating and repairing an individual condition may correct more than 1 DTC.

Scheme 486

Scheme 487

DTC P1518: THROTTLE ACTUATOR CONTROL MODULE SERIAL DATA FAULT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Throttle Actuator Control (TAC) module and the Powertrain Control Module (PCM) communicate via a dedicated serial data circuit. This serial data circuit is separate from any other serial data circuit on the vehicle. Accurate transmitting and receiving of serial data requires not only good circuit integrity but also adequate system voltage. This diagnostic test monitors the accuracy of the serial data transmitted between the TAC module and the PCM. If the PCM detects a loss of data or invalid data, this DTC sets.

1. The ignition switch is in the crank or run position.
2. The ignition voltage is greater than 5.23 volts.

1. Invalid or missing serial data messages are detected for a predetermined amount of time.
2. All of the above conditions met for more than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode; or, under certain conditions the control module commands the engine OFF.
4. The message center displays Reduced Engine Power.

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

DTC P1518 sets

1. If the battery voltage is low. If the customer's concern is slow cranking or no crank because battery voltage is low, ignore DTC P1518. Clear any DTCs from memory that may have set from the low battery voltage condition.
2. When there is a short to battery voltage on the TAC module ground circuit. Inspect the fuses for the circuits that are in the TAC module harness, (i.e., cruise or brake). An inspection of the fuses may lead you to the circuit that is shorted to the TAC module ground circuit.
3. If the TAC module ignition feed circuit is shorted to a battery voltage supply circuit. The TAC module stays powered-up when the ignition switch is turned OFF. When the ignition switch is turned ON, the TAC module is powered-up before the PCM. DTC P1518 sets because no communication is detected by the TAC module from the PCM. Inspect related circuits for being shorted to a battery voltage supply circuit.

Inspect the TAC module power and ground circuits and the TAC module/PCM serial data circuits for intermittent connections.

Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.

When the TAC module detects a problem within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual condition may correct more than 1 DTC. Remember this if you review the stored information in Capture Info.

For an Intermittent condition, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM.

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

1. 2 This step determines if the IGN relay is supplying a voltage to the ETC fuse.
2. 5 Increasing the engine speed to 3000 RPM aids in locating a shorted throttle actuator motor control circuit. Depending on the polarity of the throttle actuator motor transistors, this DTC may not set with a fault in the control circuits. The throttle actuator motor is a bi-directional DC motor. Raising the engine speed changes the polarity of the transistors in the throttle actuator motor. This occurs because 1 set of the transistors are low, 0 volts, and the other set are high, battery voltage. Therefore, if 1 set of transistors are at a low voltage and the corresponding circuit is shorted low, DTC P1518 will not set. When the polarity of the transistors change this DTC sets. If this DTC does not Fail This ignition, continue to monitor this DTC status while moving related harnesses and connectors.
3. 29 Locating and repairing an individual condition may correct more than 1 DTC.

Scheme 488

Scheme 489

Scheme 490

Scheme 491

DTC P2108: THROTTLE ACTUATOR CONTROL MODULE CIRCUIT FAULT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Throttle Actuator Control (TAC) module contains data which is essential for proper TAC system operation. The TAC module continuously tests the integrity of this data. When the TAC module is unable to write or read data to and from random access memory (RAM), or the TAC module is unable to correctly read data from the flash memory or and internal TAC module processor fault is detected, this DTC sets.

1. DTC P1518 is not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is greater than 6 volts.

1. The TAC module determines than an internal data test did not pass.
2. The above condition is met for more than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostics fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. Under certain conditions the control module commands the engine OFF.
5. The message center displays Reduced Engine Power.

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

1. Verify that the starting and charging systems are operating properly. Low system voltage can cause this DTC to set.
2. Inspect the TAC module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
3. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing an individual conditions may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

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

1. 4 Locating and repairing an individual condition may correct more than 1 DTC.

Scheme 492

DTC P2120: APP SENSOR 1 SIGNAL OR APP SENSOR 5-VOLT REFERENCE OUT OF RANGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Accelerator Pedal Position (APP) sensor 1 is a potentiometer type sensor with the following 3 circuits

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 1 signal or APP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

1. DTCs P0601, P0602, P1518, or P2108 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is more than 5.23 volts.

1. The APP sensor 1 voltage is less than 0.24 volts or more than 4.49 volts.
2. The 5-volt reference is less than 4.54 volts or more than 5.21 volts.
3. One of the above conditions is present for more than 1 second.

1. The control module stored the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. If one or more APP sensor DTCs are set, the following occurs: The control module commands Reduced Engine Power mode. The APP indicated angle is limited to a predetermined value to limit the amount or throttle control. The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. The message center displays Reduced Engine Power.

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

1. Inspect the Throttle Actuator Control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 12 This test isolates whether the short is to another TAC system circuit in the harness or within the TAC module.
2. 26 When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

Scheme 493

Scheme 494

Scheme 495

DTC P2121: APP SENSOR 1 SIGNAL AND APP SENSOR 2 SIGNAL CIRCUITS OUT OF CORRELATION

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Accelerator Pedal Position (APP) sensor 1 is a potentiometer type sensor with the following 3 circuits

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. The APP sensor 2 signal voltage is also low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 1 signal and the APP sensor 2 signal circuits are out of correlation, this DTC sets.

1. DTCs P0606, P1518 or P2108 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition volage is more than 5.23 volts.

1. APP sensor 1 disagrees with APP sensor 2 by more than 10.5 percent.
2. The above condition is present for more than 1 second.

1. The control module stored the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. If one or more APP sensor DTCs are set, the following occurs: The control module commands Reduced Engine Power mode. The APP indicated angle is limited to a predetermined value to limit the amount or throttle control. The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. The message center displays Reduced Engine Power.

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

1. Inspect the Throttle Actuator Control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 2 This step determines if a communication condition exists.
2. 5 This step isolates an internal APP sensor failure. The condition may only occur at a certain accelerator pedal position. Monitoring the APP angles for sensor 2 and sensor 3 is an accurate way of verifying the actual position of the pedal. The APP angles for all 3 sensors should be within a set percent of each other. If the pedal is at rest, the APP angle for all 3 sensors should be 0 percent. If the pedal is fully depressed, all APP angles should be 100 percent.
3. 6 The APP sensor 1 shares a common 5-volt reference circuit with the throttle position (TP) sensor 1. Monitoring the TP sensor 1 voltage aids in diagnosing the APP sensor 5-volt reference and low reference circuits. If the scan tool displays near 0 volts, the circuits are OK.
4. 9 With the TAC module still connected, this test will help determine a short to the signal circuit either within the TAC module or wiring.
5. 10 This step determines whether the TAC module or a short circuit is causing the condition.
6. 19 When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set addition DTCs. Remember this if you review the stored information in Capture Info.

Scheme 496

Scheme 497

Scheme 498

DTC P2125: APP SENSOR 2 SIGNAL OR APP SENSOR 5-VOLT REFERENCE OUT OF RANGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Accelerator Pedal Position (APP) sensor 2 is a potentiometer type sensor with the following 3 circuits

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The control module provides the APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensor then provides the control module a signal voltage proportional to pedal movement. The APP sensor 1 signal voltage is low at rest and increases as the pedal is depressed. When the control module detects that the APP sensor 2 signal or the APP sensor 5-volt reference voltage is outside the predetermined range, this DTC sets.

1. DTCs P0601, P0602, P0606, P1518 or P2108 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is more than 5.23 volts.

1. The APP sensor 2 voltage is less than 0.24 volt or more than 4.49 volts.
2. The 5-volt reference is less than 4.54 volts or more than 5.21 volts.
3. One of the above conditions is present for more than 1 second.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Lamp (MIL) will not illuminate.
3. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Failure Records.
4. If one or more APP sensor DTCs are set, the following occurs: The control module commands Reduced Engine Power mode. the APP indicated angle is limited to a predetermined value to limit the amount of throttle control. The APP indicated angle is limited to 0 percent. The control module only allows the engine to idle. The message center displays Reduced Engine Power.

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

1. Inspect the Throttle Actuator Control (TAC) module connectors for signs or water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 2 The throttle position (TP) senor 2 and the APP sensor 2 share a common 5-volt reference source. Diagnose DTC P0220 first if P0220 is also set.
2. 18 This test determines whether or not the TAC module can recognize a change in signal voltage.
3. 19 There are 2 separate 5-volt reference sources within the TAC module. The TP sensor 1 and APP sensor 1 share one 5-volt reference source. The TP sensor 2 and the APP sensor 2 share another common 5-volt reference source. The test determines whether the signal circuit is shorted to any one of the 5-volt reference circuits. If a short exists, the corresponding sensor voltage will be pulled low.
4. 20 The previous step found the signal circuit and a 5-volt reference circuit shorted together. This test isolates whether the short is in the harness or within the TAC module.
5. 26 When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

Scheme 499

Scheme 500

Scheme 501

DTC P2135: TP SENSORS NO. 1 & 2 SIGNALS DISAGREE OR SIGNAL VOLTAGES OUT OF RANGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . For intermittent conditions, see INTERMITTENT CONDITIONS . If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Throttle Position (TP) sensors 1 and 2 are potentiometer type sensors each with 3 circuits

1. A 5-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The TP sensor are used to determine the throttle plate angle for various engine management systems. The control module provides each TP sensor a 5-volt reference circuit and a low reference circuit. The TP sensors then provide the control module with signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens. When the control module detects that TP sensor 1 signal and TP sensor 2 signals disagree or signal voltages are outside the predetermined range, this DTC set.

1. DTCs P1518 or P2108 are not set.
2. The ignition switch is in the crank or run position.
3. The ignition voltage is more than 5.23 volts.

1. The TP sensor 2 disagrees with the TP sensor 1 by more than 7.5 percent.
2. The above condition is present for more than 1 second.

1. The control module illuminates the Malfunction Indicator Lamp (MIL) when the diagnostic runs and fails.
2. The control module records the operating conditions at the time the diagnostic fails. The control module stores this information in the Freeze Frame and/or the Failure Records.
3. The control module commands the TAC system to operate in the Reduced Engine Power mode.
4. Under certain conditions the control module commands the engine OFF.
5. The message center displays Reduced Engine Power.

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

1. Inspect the Throttle Actuator Control (TAC) module connectors for signs of water intrusion. If water intrusion occurs, multiple DTCs may set without any circuit or component conditions found during diagnostic testing.
2. When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.
3. For an Intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/avalanche/i-2001-2006/remont/testing-diagnostics/#engine-controls-self-diagnostics-81l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 21 When the TAC module detects a condition within the TAC system, more than 1 TAC system related DTC may set. This is due to the many redundant tests run continuously on this system. Locating and repairing 1 individual condition may correct more than 1 DTC. Disconnecting components during testing may set additional DTCs. Remember this if you review the stored information in Capture Info.

Scheme 502

Scheme 503

AVALANCHE

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SIERRA 2500HD

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SIERRA 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO 2500HD

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SILVERADO 3500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SUBURBAN

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

YUKON XL

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

See also:
• NO-START DIAGNOSIS
• SYMPTOMS
• SYSTEM & COMPONENT TESTING - 8.1L AVALANCHE, SIERRA, SILVERADO, SUBURBAN & YUKON XL
• COOLING SYSTEM TROUBLE SHOOTING
• SENSOR OPERATING RANGE CHARTS - TRUCKS
• FUEL SYSTEMS
• FUEL INJECTOR COIL TEST
• MODEL IDENTIFICATION
• DIAGNOSTIC STARTING POINT - ENGINE CONTROLS
• VEHICLE DATA RECORDER
• POWERTRAIN CONTROL MODULE
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• DTC P0601-P0607, P1600, P1621, P1627, P1680, P1681 & P1683: PCM MEMORY
• INTERMITTENT CONDITIONS
• P0420 & P0430
• P1404
• P0442
• P0446
• P0455
• P0496
• P0133 Or P0153
• P0140 Or P0160
• P1133 Or P1153
• P0135, P0141, P0155 Or P0161
• P0101
• P0102
• P0103
• P0106
• P0107
• P0108
• P0112
• P0113
• P0116
• P0116
• P0117
• P0118
• P0120
• P0125
• P0128
• P0131
• P0132
• P0134
• P0137
• P0138
• P0171
• P0172
• P0200
• P0220
• P0230
• P0300
• P0325
• P0327
• P0335
• P0336
• P0341
• P0342
• P0343
• P0351-P0358
• P0443
• P0449
• P0452
• P0453
• P0506
• P0650
• P1111
• P1112
• P1114
• P1115
• P1125
• P1172
• P1380
• P1381
• P1514
• P1515
• P1516
• P1518
• P2108
• P2120
• P2121
• P2125
• P2135
• CODE TYPES
• DRIVE CYCLES