Engine Controls Self-Diagnostics - 4.3l Chevrolet Chevy Express H2500

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 - 4.3L CHEVY EXPRESS & SAVANA article. If no DTCs are present and a driveability condition exists, proceed to TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article for diagnosis by symptom (i.e., ROUGH IDLE, ENGINE STALLS, etc.).

ON-BOARD DIAGNOSTICS

PCM is equipped with a self-diagnostic system which detects system failures or abnormalities. When a malfunction occurs, PCM will store a Diagnostic Trouble Code (DTC) and, 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 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 pre-catalyst oxygen sensor and post-catalyst 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 light or a DVOM 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 & 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 appropriate GENERATORS & REGULATORS article in STARTING & CHARGING SYSTEMS.
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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__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 DVOM connected to a suspected circuit. An abnormal reading on the DVOM 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 Vehicle Data Recorder (J 42598) is connected to the Data Link Connector (DLC) and sent with the customer. The vehicle data recorder 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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) .
2. If no DTCs are present and a driveability problem exists, see «SYMPTOMS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-trouble-shooting-no-codes-43l__symptoms) in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article. Doing so will help identify proper system or component to check in «SYSTEM & COMPONENT TESTING - 4.3L CHEVY EXPRESS & SAVANA»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-control-system-component-tests-43l) 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 engine control system. The Diagnostic System Check must be the starting point for any driveability concern. The Diagnostic System Check directs the service technician to the next logical step in order to diagnose the concern. Understanding and correctly using the diagnostic table reduces diagnostic time, and prevents the replacement of good parts.

Test Description

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

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. 5 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. 6 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. 8 If there are other modules with DTCs set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__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. 10 This step is for areas that have inspection and maintenance testing procedures for emissions testing. Use this step if the testing facility found one or more I/M system 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 STARTING & CHARGING SYSTEMS. 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.

Scheme 60

Scheme 61

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 Instrument Panel Cluster (IPC) or Powertrain Control Modules (PCM) have 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 listed control modules. If you are using a Tech 2(R), obtain the information using the Class 2 Message Monitor feature: Instrument Panel Cluster (IPC). PCM. 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.
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/chevy-express-h2500/2003-2003/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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__diagnostic-trouble-code-definitions) .

RETRIEVING DIAGNOSTIC TROUBLE CODES

DTCs are retrieved using a Tech 2(R) 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. PCM adaptive learning and system monitors will only be cleared for those system which had a stored DTC.

Disconnect Battery

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

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

Warm-up Cycles

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

SCAN TOOL USAGE

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

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

A problem may exist even if DTCs are not present. About 80 percent of driveability problems occur without setting DTCs. Sensors that are out of calibration will not set a DTC but will cause driveability problems.

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

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

Scan Tool Display

Note. OBD-II vehicles have options available in the scan tool DTC mode to display enhanced information available. However, to fully utilize information and procedures requires the use of a Tech 2(R) scan tool. See scan tool operator's manual for additional information.

The following are Tech 2(R) scan tool sub-menus in the DTC INFO and SPECIFIC DTC modes

1. DTC INFO MODE Used to search for specific type of stored DTC information. There are 7 choices in this mode. Technician may be instructed to test DTCs in a certain manner. Follow the affected DTC test procedures. To get complete description of any status, hit ENTER key before pressing the desired "F" key.
2. DTC STATUS This selection will display any DTCs that have not run during the current ignition cycle or have reported a test failure during this ignition up to a maximum of 33 DTCs. A DTC test that runs and passes will cause affected DTC to be removed from scan tool screen.
3. FAIL THIS IGN. This selection will display all DTCs that have failed during the present ignition cycle.
4. HISTORY This selection will display only DTCs that are stored in the control module's history memory. It will not display type "D" DTCs. It will display all type "A" and type "B" DTCs that have the MIL illuminated and have failed within the last 40 warm-up cycles. It will also display type "C" DTCs that have failed within the 40 warm-up cycles.
5. LAST TEST FAIL This selection will only display DTCs that have failed the last time the test ran. If type "A" or "B" DTCs are displayed, the last test may have ran during the previous ignition cycle. For type "C" DTCs, the last failure must have occurred during the current ignition cycle to be displayed as LAST TEST FAIL.
6. MIL REQUEST This selection will only display DTCs that are requesting MIL illumination. Type "C" DTCs cannot be displayed using this option. This selection will report type "B" DTCs only after MIL illumination has been requested.
7. NOT RUN SCC Not Run Since Code Clear option will display up to 33 DTCs that have not run since DTCs were last cleared. Since any displayed DTCs have not run, their condition (passing or failing) is unknown.
8. TEST FAIL SCC Test Fail Since Code Clear selection will display all active and history DTCs that have reported a test failure since the last time DTCs were cleared. DTCs that last failed over 40 warm-up cycles before this option is selected will not be displayed.
9. FAILED SINCE CLEAR This message indicates the DTC has failed at least once within the last 40 warm-up cycles since the last time DTCs were cleared.
10. NOT RUN SINCE CL. Not Run Since Cleared message indicates that the selected diagnostic test has not run since the last time DTCs were cleared. Therefore, the diagnostic test status (passed or failed) is unknown. After DTCs are cleared, this message will continue to be displayed until the diagnostic test runs.
11. NOT RUN THIS IGN. Not Run This Ignition message indicates the selected diagnostic test has not run this ignition cycle.
12. TEST RAN AND PASSED This message indicates the selected diagnostic test has: Passed the last test. Ran and passed during this ignition cycle. Ran and passed since DTCs were last cleared. Test has not failed since DTCs were last cleared. If this message is displayed, repair is complete. If FAILED THIS IGN. message is displayed, repair is incomplete and further diagnosis is required.

POWERTRAIN CONTROL MODULE LOCATION

Powertrain Control Module (PCM) is located on left fender in engine compartment. See COMPONENT LOCATIONS .

CKP SYSTEM VARIATION LEARN PROCEDURE

Note. For additional diagnostic information, see DTC P0336: CRANKSHAFT POSITION SENSOR CIRCUIT PERFORMANCE .

1. Install a scan tool.
2. With a scan tool, monitor the powertrain control module for DTCs. If other DTCs are set, except DTC P0315, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__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 throttle when fuel cut-off occurs. Engine should not accelerate beyond calibrated RPM value. Release throttle immediately if value is exceeded. Block drive wheels. Set parking brake. DO NOT apply brake pedal. Cycle the ignition from OFF to ON. Apply and hold the brake pedal. Start and idle engine. Turn A/C OFF. 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 Sensor (CKP) Sensor 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 engine coolant temperature is not warm enough, idle the engine until the engine coolant temperature reaches the correct temperature.
5. With the scan tool, enable the crankshaft position system variation learn procedure.
6. Accelerate to WOT.
7. Immediately release the throttle when fuel cut-off is reached.
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, see «DTC P0315»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__dtc-p0315-crankshaft-position-system-variation) . If any other DTCs set, refer to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__diagnostic-trouble-code-definitions) for the applicable DTC.
9. Turn OFF the ignition for 30 seconds after the learn procedure is completed successfully.

POWERTRAIN CONTROL MODULE

Note. Programing Powertrain Control Module requires a compatible scan tool and a Techline(R) terminal. Procedure uses a Tech 2(R) scanner.

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. Turn OFF the ignition.
2. Install the Tech 2(R) to the Data Link Connector (DLC), with the Tech 2(R) turned OFF.
3. Turn ON Tech 2(R). Press ENTER at title screen.
4. Turn ON the ignition, with the engine OFF.
5. Turn OFF all vehicle accessories.
6. Select SERVICE PROGRAMMING SYSTEM at the MAIN MENU.
7. Select REQUEST INFO.
8. Enter the vehicle description by following the on-screen instructions.
9. Verify that the correct VIN is entered on the Tech 2(R) and select YES.
10. Turn OFF the Tech 2(R).
11. Disconnect the Tech 2(R) from the vehicle.
12. Turn OFF the ignition.
13. Connect the Tech 2(R) to the terminal.
14. Launch the TIS application at the terminal.
15. Select the SERVICE PROGRAMMING SYSTEM at the main screen.
16. Highlight the following information on the Select Diagnostic Tool and Programming Process Screen: Select DIAGNOSTIC TOOL, then select Tech 2(R). 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.
17. Select NEXT.
18. Verify the connections and select NEXT.
19. Verify the VIN and select NEXT.
20. Select the appropriate controller for the vehicle being serviced.
21. 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/or axle ratios.
22. Select NEXT.
23. Select the appropriate calibration file for the vehicle being serviced.
24. Select NEXT.
25. Verify your selection on the Summary screen.
26. Select NEXT.
27. Perform the CRANKSHAFT POSITION VARIATION RELEARN PROCEDURE using the SPECIAL FUNCTIONS feature, if applicable.
28. Close the application and return to the TIS APPLICATION SELECTION screen after the download is complete.
29. Turn OFF the Tech 2(R).
30. Disconnect the Tech 2(R) from the terminal.
31. Connect the Tech 2(R) to the vehicle DLC, with the engine and the Tech 2(R) OFF.
32. Turn ON the Tech 2(R).
33. Press ENTER at the TITLE screen.
34. Turn ON the ignition, with the engine OFF.
35. Select SERVICE PROGRAMMING SYSTEM.
36. Select the PROGRAM ECU function on the Tech 2(R).
37. Verify the VIN and calibration numbers, select CONTINUE.
38. Follow the on-screen instructions and select CONTINUE.
39. Select CONTINUE and exit the program after the Tech 2(R) displays PROGRAMMING WAS SUCCESSFUL.
40. Turn OFF the ignition.
41. Turn OFF the Tech 2(R).
42. Disconnect the Tech 2(R) from the vehicle.
43. Verify the control module programming was successful. Turn OFF the ignition for 30 seconds.
44. Start the engine. Repeat the Service Programming System procedure if the vehicle does not start or starts but runs rough.

Off-Board 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, then select Tech 2(R). 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 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(R).
7. Select the SERVICE PROGRAMMING REQUEST INFORMATION function on the Tech 2(R).
8. Follow the Tech 2(R) instructions to obtain the module data and security information.
9. After the Tech 2(R) has received the data from the module, exit the Request Info mode.
10. Disconnect the Tech 2(R) from the OBPA.
11. Turn OFF the Tech 2(R).
12. Connect the Tech 2(R) to the terminal.
13. Turn ON the Tech 2(R).
14. Select NEXT at the terminal after the Tech 2(R) start-up screen appears.
15. Enter the VIN of the vehicle that will be receiving the control module.
16. Select NEXT.
17. 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/or axle ratios.
18. Select NEXT.
19. Select a calibration on the Calibration Selection screen, if necessary.
20. Ensure all the desired folder tabs have a green check mark.
21. Select NEXT.
22. Verify the current and the selected calibration of the control module on the Summary screen.
23. Select NEXT.
24. Select OK.
25. On model year 1996 and newer controllers, a Crankshaft Position (CKP) relearn procedure box may appear. Select OK.
26. Follow the on-screen instructions, if any, when the Program Controller/Programming Complete screen appears.
27. Select CLOSE.
28. Turn OFF the Tech 2(R).
29. Disconnect the Tech 2(R) from the terminal.
30. Connect the Tech 2(R) to the OBPA.
31. Turn ON the Tech 2(R).
32. Select Enter at the title screen.
33. Select the SERVICE PROGRAMMING SYSTEM at the Main Menu.
34. Select the PROGRAM ECU function.
35. Select CONTINUE.
36. Follow the on-screen instructions.
37. Select Continue.
38. Select EXIT when the programming is complete.
39. Turn OFF the OBPA.
40. Turn OFF the Tech 2(R).
41. Disconnect the OBPA from the Tech 2(R) 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, 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 OFF-BOARD PROGRAMMING ADAPTER.
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 the OBPA. The Tech 2(R).
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/or axle ratios.
14. Select NEXT.
15. Select a calibration on the Calibration Selection screen, if necessary.
16. Ensure all the desired folder tabs have a green check mark.
17. Select NEXT.
18. Verify the current and the selected calibration of the control module on the Summary screen.
19. Select NEXT.
20. Select OK.
21. On model year 1996 and newer controllers, a Crankshaft Position (CKP) relearn procedure box may appear. Select OK.
22. Follow the on-screen instructions, if any, when the Program Controller/Programming Complete screen appears.
23. Select CLOSE.
24. Turn OFF the OBPA.
25. Turn OFF the Tech 2(R).
26. Disconnect the OBPA from the Tech 2(R) 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(R).
23. Disconnect the Tech 2(R) from the vehicle.

THEFT DETERRENT PASSWORD LEARN PROCEDURE

Note. If replacing the Passlock(R) module with a GM Service Parts Operations (SPO) replacement part, the module will learn Passlock(R) sensor data code immediately. The existing PCM however, must learn the new fuel continue password when the Passlock(R) module 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(R) Sensor
2. Passlock(R) Module
3. PCM

10 Minute Learn Procedure

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

1. Connect the Tech 2(R) to the vehicle.
2. Select "Request Information" under "Service Programming".
3. Disconnect the Tech 2(R) from the vehicle and connect it to a Techline(R) terminal.
4. On the Techline(R) terminal, select "Theft Module Re-Learn" under "Service Programming".
5. Disconnect the Tech 2(R) from the Techline(R) terminal and connect it to the vehicle.
6. Turn ON the ignition, with the engine OFF.
7. Select "VTD Re-Learn" 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(R) 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(R) (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(R) 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(R) 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 Inspection/Maintenance (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 Light (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.

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

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.

Scheme 62

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.

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 Emission (EVAP) system from initiating. If a step is interrupted before completion, perform the remaining portion of the set procedures. Any portion of the set procedure that requires the engine at operating temperature may be repeated. This allows most of the diagnostics to run and the remaining tests can be performed using the individual System Set Procedures. If 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 numbers below refer to the step numbers in the diagnostic procedures.

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 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 (if equipped). 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.

Scheme 63

Scheme 64

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the catalyst system. The test may be used to set the I/M System Status indicators to YES. Ensure 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 control module runs a maximum of 6 tests per trip until the Catalyst System Status updates to YES. If the status does not update, the test outlined in this procedure can be repeated until the I/M System Status updates to YES. The I/M System Status does not indicate whether the test has passed or failed, only that a decision was made. When all of the diagnostics for a specific system have run and passed, the I/M System Status will update to YES. If a test for a specific system has failed, the I/M System Status will update to YES, indicating a determination was made, even if all of the required tests have not run. When a failure occurs, the Emission Related DTC portion of the I/M System Status display will indicate the Malfunction Indicator Light (MIL) is requested. The I/M System Status also registers the number of Diagnostic Trouble Codes (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 in the diagnostic procedures.

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 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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) .
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.

Scheme 65

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. 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, 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 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, AND P0496 are not set.
2. The Barometric (BARO) 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 test will initiate only after a cold start. The control module considers the engine to be cold if the following conditions are met: The Engine Coolant Temperature (ECT) is between 39-86° F (3.75-30° C). The Intake Air Temperature (IAT) is between 39-86° F (3.75-30° C). 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 the cooling fan or an A/C compressor clutch turning ON, may cause the test to abort.

Scheme 66

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 9-18 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 Light (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 procedures.

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 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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l) .
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.

Scheme 67

The purpose of this test is to satisfy the enable criteria necessary to execute I/M readiness diagnostics for the Heated Oxygen Sensor (HO2S) Heater System. The test may be used to set the I/M System Status to YES. The I/M System Status Display on the scan tool provides an indication of whether 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 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.

1. The start-up Engine Coolant Temperature (ECT) is less than 122°F (50°C).
2. The start-up Intake Air Temperature (IAT) is less than 122°F (50°C).
3. The difference between the IAT and the ECT is less than 14°F (8°C).
4. The battery voltage is between 11-18 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, it may have failed or aborted due to the loss of enabling conditions. Extremely high ambient temperatures may prevent the HO2S Heater Test from initiating. 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.

Scheme 68

SUMMARY

If no hard fault DTCs are present, driveability symptoms exist or intermittent DTC(s) exist, diagnosis by symptom (i.e., ROUGH IDLE, NO START, etc.). See SYMPTOMS in TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA article.

DIAGNOSTIC TROUBLE CODE DEFINITIONS

DIAGNOSTIC TROUBLE CODE INDEX

Scheme 69

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Scheme 71

Scheme 72

Scheme 73

Scheme 74

Scheme 75

Scheme 76

Scheme 77

Scheme 78

Scheme 79

Scheme 80

Scheme 81

Scheme 82

Scheme 83

Scheme 84

Scheme 85

Scheme 86

Scheme 87

Scheme 88

Scheme 89

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Scheme 96

Scheme 97

MALFUNCTION INDICATOR LIGHT INOPERATIVE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Battery positive voltage is supplied directly to the Malfunction Indicator Light (MIL). The Powertrain Control Module (PCM) turns the MIL ON by grounding the MIL control circuit. There should be a steady MIL with the ignition ON and the engine OFF.

MIL Operation

The Malfunction Indicator Light (MIL) is located on the instrument panel.

MIL Function

1. The MIL informs the driver that a malfunction has occurred and the vehicle should be taken in for service as soon as possible.
2. The MIL illuminates during a bulb test and a system test.
3. A Diagnostic Trouble Code (DTC) will be stored if a MIL is requested by the PCM.

MIL Illumination

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

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

1. 4 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 98

Scheme 99

MALFUNCTION INDICATOR LIGHT ALWAYS ON

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

Battery positive voltage is supplied directly to the Malfunction Indicator Light (MIL). The Powertrain Control Module (PCM) turns the MIL ON by grounding the MIL control circuit.

The Malfunction Indicator Light (MIL) is located on the instrument panel.

MIL Function

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

MIL Illumination

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

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

1. 2 This step determines if the condition is with the MIL control circuit or the PCM.

Scheme 100

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 P0016: CRANKSHAFT POSITION-TO-CAMSHAFT POSITION CORRELATION

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) supplies a 12-volt reference circuit and a low reference circuit to both the Crankshaft Position (CKP) sensor and the Camshaft Position (CMP) sensor. The CKP sensor sends a signal to the PCM with each revolution of the camshaft. This Diagnostic Trouble Code (DTC) monitors the CKP signal and the CMP signal to determine if they are synchronized. If both signals are not observed by the PCM within a narrow period of time, the PCM will determine that an error has occurred and DTC P0016 will set.

Conditions For Running DTC

The engine is running.

Conditions For Setting DTC

When the engine is running, the cam sensor pulse is not detected at the correct relative position to the crankshaft position sensor pulse.

Action Taken When DTC Sets

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

Conditions For Clearing MIL/DTC

1. The PCM turns OFF the 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.

Check for one of the following

1. A loose or missing distributor hold down bolt.
2. Loose CMP sensor causing a variance in the sensor signal.
3. An incorrectly installed distributor - one tooth off in either advance or retard positions.
4. A loose distributor rotor on the distributor shaft.
5. Excessive free play in the timing chain and gear assembly.

If an intermittent condition is suspected, see

INTERMITTENT CONDITIONS

under SELF-DIAGNOSTIC SYSTEM.

Scheme 101

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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. 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 Coolant Temperature (ECT).
4. 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. If the PCM detects the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value DTC P0101 sets.

1. DTCs P0102, P0103, P0106, P0107, P0108, P0121, P0122, P0123, P0443, P0446, P0449, P0455, P0496 are not set.
2. The engine is cranking or running.
3. The ignition 1 signal is between 11 volts and 18 volts.
4. The Throttle Position (TP) sensor angle is less than 95 percent.
5. The change in the TP sensor angle is less than 5 percent.
6. The MAP sensor is less than 80 kPa.
7. The change in the MAP sensor is less than 3 kPa.
8. The above conditions are met for 1.5 seconds.

The PCM detects that the actual MAF sensor frequency signal is not within a predetermined range of the calculated MAF value for more than 4.0 seconds.

1. The 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 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.

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 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 150 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. Inspect for a skewed or stuck ECT sensor.
8. 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 BARO sensor value is continually updated near wide open throttle. A skewed MAP sensor will cause the calculated mass air flow value to be inaccurate and may result in a no start condition. 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 1,000 ft. (305 m) of altitude.
9. A high resistance on the 5-volt reference circuit of the MAP sensor may cause this DTC to set.
10. A high resistance on the low reference circuit of the MAP sensor may cause this DTC to set.

Condition may be related to aftermarket accessories. 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 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 sensor is 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 102

Scheme 103

Scheme 104

ALTITUDE VS. BAROMETRIC PRESSURE

DTC P0102: MAF SENSOR CIRCUIT - LOW FREQUENCY

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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. If the PCM detects the frequency signal is less than the possible range of the correctly operating MAF sensor DTC P0102 sets.

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 frequency is stable for more than 0.7 second.

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

1. The control module illuminates the Malfunction Indicator Light (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 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.

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. Inspect for any contamination or debris on the sensing elements of the MAF sensor.
3. A wide open throttle acceleration from a stop should cause the MAF sensor parameter on the scan tool to increase rapidly. This increase should be from 3-10 g/s at idle to 150 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.
4. A high resistance of 15 Ohms or more on the ground circuit of the MAF sensor can cause this DTC to set. A high resistance may cause a driveability concern before this DTC sets.

Condition may be related to aftermarket accessories. 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 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. 13 This step will determine which portion of the circuit or which component is shorted to ground.
6. 16 This step verifies that the signal circuit is not shorted to any other PCM circuit.

Scheme 105

Scheme 106

Scheme 107

DTC P0103: MAF SENSOR CIRCUIT - HIGH FREQUENCY

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 frequency signal in order to provide the correct fuel delivery for a wide range of engine speeds and loads. A small quantity of air entering the engine indicates a deceleration or idle. A large quantity of air entering the engine indicates an acceleration or high load condition. The MAF sensor has 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. If the PCM detects a frequency signal more than the possible range of a correctly operating MAF sensor DTC P0103 sets.

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 frequency 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 Light (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 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. 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 can cause a DTC P0103 to set.

Condition may be related to aftermarket accessories. 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 tests for Electromagnetic Interference (EMI) on the signal circuit of the MAF sensor. A frequency reading with the MAF sensor disconnected may indicate 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 108

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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. If the PCM detects that the MAP sensor signal is not within the predicted range, DTC P0106 sets.

1. DTCs P0101, P0102, P0103, P0107, P0108, P0121, P0122, P0123, P0442, P0443, and P0446 are not set.
2. The engine is running.
3. The engine speed is between 400-5000 RPM.
4. The change in engine speed is less than 125 RPM.
5. The traction control is not active.
6. A change in idle air is less than 10 g/s.
7. The A/C compressor clutch states does not change.
8. The power steering load is stable.
9. The brake switch state does not change.
10. The above conditions are met for 1 second.

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

1. The control module illuminates the Malfunction Indicator Light (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 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. 5 This step tests the MAP sensor's ability to correctly indicate barometric pressure.
2. 7 This step tests the MAP sensor's ability to respond to an increase in engine vacuum.
3. 9 This step tests for a proper MAP sensor pressure with an applied vacuum.

Scheme 109

Scheme 110

Scheme 111

Scheme 112

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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. If the PCM detects a MAP sensor signal voltage that is excessively low, DTC P0107 will set.

1. The ignition is ON.
2. DTCs P0121, P0122, or P0123 are not set.
3. The throttle angle is more than 0 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.

MAP sensor voltage is less than 0.10 volt for more than 2 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 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 aid in locating an intermittent condition.
2. 5 This step determines if voltage is available to the sensor. It also determines if there is sufficient current flow in the circuit.

Scheme 113

Scheme 114

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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. If the PCM detects a MAP sensor signal voltage that is excessively high, DTC P0108 will set.

1. The engine has been running for a length of time that is determined by start-up coolant temperature. The length of time ranges from 5.5 minutes at less than -22°F (-30°C) to 10 seconds at more than 86°F (30°C).
2. DTCs P0121, P0122, or P0123 are not set.
3. The throttle angle is less than 1 percent when the engine speed is less than 1200 RPM; or, the throttle angle is less than 12.5 percent when the engine speed is more than 1200 RPM.

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

1. The control module illuminates the Malfunction Indicator Light (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 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 number below refers to the step number on 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 data can aid in locating an intermittent condition.

Scheme 115

Scheme 116

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 low IAT signal voltage, indicating a high temperature, DTC P0112 sets.

1. DTCs P0502, or 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 (40 km/h).

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

1. The control module illuminates the Malfunction Indicator Light (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 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.

Scheme 117

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 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, or 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 (11 km/h).
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 IAT sensor signal voltage indicates that the intake air temperature is less than -36°F (-38°C) for more than 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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.

Scheme 118

Scheme 119

DTC P0116: ECT SENSOR PERFORMANCE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 engine coolant temperature is low, resistance is high. When the engine coolant temperature is high the resistance is low. The PCM uses this High Side Coolant Rationality test to determine if the ECT input is skewed high. 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 and engine block heater. If the PCM detects that the temperature difference between the ECT and the IAT is not within the calibrated range after the ignition OFF time, DTC P0116 sets.

1. The ignition is ON.
2. The IAT Sensor parameter is more than 59°F (15°C).
3. DTCs P0112, P0113, P0117, P0118, P0125, P0128, P0601, P0602 or P1683 are not set.
4. The vehicle has a minimum soak time of 10 hours.
5. This DTC will run once during the ignition cycle within the enabling conditions.

If the PCM detects a temperature difference of more than 27°F (15°C) between the ECT and the IAT, the vehicle must be driven for 8 minutes over 15 MPH. If the IAT sensor temperature decreases more than 5°F (3°C) then a block heater is indicated and the test is aborted. If the IAT temperature does not decrease, a block heater was not detected and DTC P0116 sets.

1. The control module illuminates the Malfunction Indicator Light (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 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 procedures.

1. 7 A snapshot is the quickest method to capture the data before it changes.
2. 8 An IAT sensor that is skewed low can cause this DTC to set.
3. 10 This step will determine if high resistance has caused this DTC to set.
4. 12 A high resistance short from the signal circuit to the low reference circuit can cause this DTC to set.

Scheme 120

Scheme 121

Scheme 122

Scheme 123

SENSOR TEMPERATURE VS. RESISTANCE

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 and 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 low ECT signal voltage, which is a high temperature indication, this Diagnostic Trouble Code (DTC) P0117 will set.

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

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

1. The control module illuminates the Malfunction Indicator Light (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 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.

Scheme 124

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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. 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 more than 60 seconds, or 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 Light (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 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.

Scheme 125

Scheme 126

DTC P0121: TP SENSOR PERFORMANCE

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

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with the following circuits

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

The PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit and a ground on the low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. When the conditions for running this DTC are met, the PCM will use the MAP sensor in order to determine if the predicted operating range of the TP sensor is correct. If the PCM detects the TP sensor voltage is out of the predicted range, DTC P0121 sets.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0122, P0123, P0506, and P0507 are not set.
2. The engine is running for more than 2 minutes.
3. The Engine Coolant Temperature (ECT) is more than 158°F (70°C).
4. The MAP is less than 43 kPa for a TP sensor skewed high test.
5. The MAP is more than 67 kPa for a TP sensor skewed low test.
6. The MAP is steady for 2 seconds or more.
7. The TP does not vary more than 1.5 percent for 2 seconds or more.

1. The PCM detects that the TP sensor voltage is more than a predicted value when the MAP is less than 43 kPa.
2. The PCM detects that the TP sensor voltage is less than a predicted value when the MAP is more than 67 kPa.
3. The above conditions are present for 1 second.

1. The control module illuminates the Malfunction Indicator Light (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 the MIL/DTC

1. The 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.

Scheme 127

Scheme 128

Scheme 129

DTC P0122: TP SENSOR CIRCUIT - LOW VOLTAGE

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

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) in order to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits

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

The PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. If the PCM detects an excessively low signal voltage, Diagnostic Trouble Code (DTC) P0122 will set.

The ignition is ON.

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

1. The control module illuminates the Malfunction Indicator Light (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 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 number below refers to the step number in the diagnostic procedure.

1. 5 This step determines if voltage is available to the sensor. It also determines if there is sufficient current flow in the circuit.

Scheme 130

Scheme 131

DTC P0123: TP SENSOR CIRCUIT - HIGH VOLTAGE

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

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits

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

The PCM provides the TP sensor with a 5-volt reference circuit and a low reference circuit. The PCM provides the TP sensor with 5 volts on the 5-volt reference circuit and a ground on the low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts throughout the TP sensor signal circuit. If the PCM detects an excessively high signal voltage, DTC P0123 sets.

1. The ignition is ON.
2. DTCs P0641 and P0651 are not set.

The PCM detects that the TP sensor voltage is less than 4.9 volt for more than 1 second.

1. The control module illuminates the Malfunction Indicator Light (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 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 number below refers to the step number in the diagnostic procedures.

1. 6 Each terminal in the connector must be jumpered to its respective mate in the sensor. This allows the sensor to operate and permits access to the low reference circuit for the voltage drop measurement.

Scheme 132

Scheme 133

DTC P0125: EXCESSIVE TIME TO ENTER CLOSED LOOP FUEL CONTROL

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS 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. The air flow coning into the engine is accumulated and used to determine if the vehicle has been driven within the conditions that would allow the engine coolant to heat up normally to 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 P0100, P0102, P0103, P0112, P0113, P0116, P0117, P0118, P0500, P0502 or P503 are not set.
2. The Intake Air Temperature (IAT) is between 19-131° F (-7-+55° C).
3. The start-up coolant temperature is between -33-+83° F (-36-+28.5° C).
4. The mass air flow is between 24-75 g/s with the average 12 g/s.
5. The vehicle speed is more than 5 mph (8 km/h) for more than 0.5 miles (0.80 km).
6. The engine is running between 120-3200 seconds.

The PCM detect that

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 amount of engine air flow has been met.
4. The engine coolant temperature for Closed Loop of 93° F (34° C) has not been met.

1. The control module illuminates the Malfunction Indicator Light (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 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.

Scheme 134

Scheme 135

DTC P0128: ECT LESS THAN THERMOSTAT REGULATING TEMPERATURE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis requires testing of sensor operating range, see appropriate table in SENSOR OPERATING RANGE CHARTS - TRUCKS 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, P0103, P0112, P0113, P0116, P0117, P0118, P0125, P0500, P0502 or P0503 are not set.
2. The coolant temperature is less than 149° F (65° C).
3. The Air Intake Temperature (IAT) is 19-131° F (-7 to 55°C) or more.
4. The engine is running more than 2 minutes and less than 17 minutes.
5. The vehicle speed is more than 5 MPH for more than 1.5 miles (2.5 km).
6. The Mass Air Flow (MAF) average reading is between 24-75 g/s with the average more than 12 g/s.

The PCM detects that

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 or 158° F (70° C) has not been met.

1. The control module illuminates the Malfunction Indicator Light (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 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.

Scheme 136

Scheme 137

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P496 are not set.
2. The loop status is closed.
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The Fuel Tank Level Remaining parameter is more than 10 percent.
5. The TP sensor parameter is between 3-70 percent.

Power Enrichment Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P496 are not set.
2. The Loop Status parameter is closed.
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The Fuel Tank Level Remaining parameter 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 PCM detects that the affected HO2S voltage parameter is less than 200 mV for 165 seconds.

Power Enrichment Test

1. The PCM detects that the affected HO2S voltage parameter is less than 400 mV for 10 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 the Loop Status open.

1. The 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.

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

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

Scheme 138

Scheme 139

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P496 are not set.
2. The Loop Status parameter is closed.
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The Fuel Tank Level Remaining parameter is more than 10 percent.
5. The Throttle Position (TP) Sensor parameter is between 3-70 percent.

Decel. Fuel Cutoff Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P496 are not set.
2. The Loop Status parameter is closed.
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The Fuel Tank Level Remaining parameter 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 900 mV for 165 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 Light (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 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 Loop Status Open.

1. The 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.

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

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

Scheme 140

Scheme 141

Scheme 142

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 high 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 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0133 & P0153 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0200, P0300, P0442, P0446, P0452, P0453, P0455 and P0496 are not set.
2. The Engine Coolant Temperature (ECT) sensor is more than 140°F (60°C).
3. The EVAP Purge Solenoid Command parameter is more than 1 percent.
4. The MAF Sensor parameter is between 18-55 g/s.
5. The Engine Speed parameter is between 1200-3000 RPM.
6. The TP Sensor parameter is more than 5 percent.
7. The Loop Status parameter is closed.
8. The Ignition 1 Signal parameter is between 10-18 volts.
9. The Fuel Tank Level Remaining parameter is more than 10 percent.
10. The Engine Run Time parameter is more than 160 seconds.
11. The above conditions are met for 100 seconds.

The PCM detects that the affected HO2S rich-to-lean or lean-to-rich average response time is more than a calibrated value.

1. The control module illuminates the Malfunction Indicator Light (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 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 procedures.

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

Scheme 143

Scheme 144

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 high 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 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0134 & P0154 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P0496 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 Light (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 the Loop Status Open.

1. The 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.

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

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

Scheme 145

Scheme 146

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. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 high 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 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0135 & P0141, P0155 or P0161 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455, or P0496 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 2.5 amps or less the 0.25 amps.
2. The above condition is met for 10 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 procedures.

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

Scheme 147

Scheme 148

Scheme 149

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 high 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 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0137 or P0157 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P0496 are not set.
2. The Loop Status parameter is closed.
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The Fuel Tank Level remaining parameter 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 PCM detects that the affected HO2S voltage parameter is less than 80 mV for 200 seconds.

Power Enrichment Test

1. The PCM detects that the affected HO2S voltage parameter is less than 490 mV for 10 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 procedures.

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

Scheme 150

Scheme 151

Scheme 152

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 high 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 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0138 or P0158 will set.

Rich Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455, or P0496 are not set.
2. The Ignition 1 signal is between 10-18 volts.
3. The fuel tank level remaining is more than 10 percent.
4. The Loop Status is closed.
5. The TP Sensor parameter is between 3-70 percent.

Decel Fuel Cut-off Test Enable

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0200, P0300, P0442, P0446, P0452, P0453, P0455, or P0496 are not set.
2. The Loop Status parameter is closed.
3. The Ignition 1 Signal parameter is between 10-18 volts.
4. The Fuel Tank Level remaining parameter 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 Light (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 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 procedures.

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

Scheme 153

Scheme 154

Scheme 155

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 high 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 200 mV or from blow 200 mV to above 600 mV. If the PCM detects that the transition time is too long, DTCs P0140 or P0160 will set.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0141, P0161, P0200, P0300, P0442, P0446, P0452, P0453, P0455, or P0496 are not set.
2. The Engine Run Time parameter is more than 300 seconds.
3. The Loop Status is closed.
4. The Ignition 1 Signal parameter is between 10-18 volts.

1. The PCM detects that the affected HO2S voltage parameter is between 410-490 mV for 150 seconds.
2. The TP Sensor parameter changes more than 5 percent within 1 second, 6 time.

1. The control module illuminates the Malfunction Indicator Light (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 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 procedures.

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

Scheme 156

Scheme 157

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 air/fuel ratio of 14.7:1. If the PCM detects an excessively lean condition, Diagnostic Trouble Code (DTC) P0171 or P0174 will set.

1. DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
2. The Engine Coolant Temperature (ECT) is between 167-239°F (75-115°C).
3. The intake air temperature is between 4-194°F (-20 to 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 (BARO) pressure is more than 10.7 psi (74 kPa).
8. The Mass Air Flow (MAF) is between 5-90 g/s.
9. The fuel level is more than 10 percent.
10. The throttle position 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 Light (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 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 procedures.

1. 5 If conditions were not corrected, see «BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) 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 158

Scheme 159

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 deliver y based on sensor signals without Oxygen Sensor (O2S) input. During Closed Loop, the oxygen sensor inputs are added and used by the PCM to calculate short and long term fuel trim fuel delivery adjustments. If the O2S indicate a lean condition, the fuel trim values will be above 0 percent. If the O2S indicate a rich condition, the 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 Emission (EVAP) canister is causing a rich condition. If the PCM detects an excessively rich condition, DTC P0172 or P0175 sets.

1. DTCs P0101, P0103, P0108, P0135, P0137, P0141, P0200, P0300, P0410, P0420, P0430, P0440, P0442, P0443, P0446, P0449, P0506, P0507 or P1441 are not set.
2. The Engine Coolant Temperature (ECT) is between 167-239°F (75-115°C).
3. The intake air temperature is between 4-194°F (-20 to 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 400-3,000 RPM.
7. The Barometric (BARO) pressure is more than 10.7 psi. (74 kPa) .
8. The Mass Air Flow (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. The above conditions are present for 40 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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. Fuel contamination, such as water and alcohol, will affect 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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__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/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 5 If conditions were not corrected, see «BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-basic-diagnostic-procedures) article.
2. 6 An EVAP canister that is saturated will cause a rich condition. Fuel in the vacuum line to the fuel pressure regulator indicates a bad regulator. If conditions were not corrected, a worn cam, worn intake or exhaust valves, or other engine mechanical failure may be at fault.

Scheme 160

Scheme 161

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The control module enables the appropriate fuel injector pulse 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 is running.
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 Light (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 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. Performing the Fuel Injector Coil test may help isolate an intermittent condition. See appropriate SYSTEM & COMPONENT TESTING article.
2. For an intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

Scheme 162

Scheme 163

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump within 2 seconds if ignition reference pulses cease to be detected and the ignition remains ON. The control module monitors the voltage on the fuel pump relay control circuit. If the control module detects an incorrect voltage on the fuel pump relay control circuit, a fuel pump relay 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 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 Light (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 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. Use a scan tool in order to clear the MIL and the DTC.

Scheme 164

Scheme 165

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 (TWC) to overheat under certain driving conditions. The Malfunction Indicator Light (MIL) will flash ON and OFF when the conditions for catalytic converter overheating are present. If the PCM detects a misfire rate sufficient to cause emission levels to exceed mandated standards, DTC P0300 will set.

1. DTCs P0016, P0101, P0102, P0103, P0116, P0117, P0118, P0125, P0128, P0315, P0335, P0336, P0341, P0502, P0503, P1114, P1115, or P1121 are not set.
2. The fuel level is more than 10 percent.
3. Then engine speed is between 450-5000 RPM.
4. The ignition voltage is between 10-18 volts.
5. The Engine Coolant Temperature (ECT) is between 19-266° F (-7-130° C).
6. The throttle angle is steady within 1 percent.
7. The Anti-lock Brake System (ABS) and the Traction Control System (TCS) 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 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 Light (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 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.

Excessive vibration from sources other than the engine could cause DTC P0300 to set. The following are possible sources of vibration

1. Variable thickness brake rotors.
2. Drive shaft not balanced.
3. Worn or damaged accessory drive belt.

There may be more or less cylinders actually misfiring than indicated by the scan tool. Spray water on the secondary ignition components using a spray bottle. Look and listen for arcing or misfiring.

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

1. 2 If the actual CKP variation values are not within the learned values, the misfire counters may increment.

Scheme 166

Scheme 167

Scheme 168

DTC P0315: CRANKSHAFT POSITION SYSTEM VARIATION NOT LEARNED

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Crankshaft Position (CKP) system variation learn feature is used to calculate referenced period errors caused by slight tolerance variations in the crankshaft and the CKP sensors. The calculated error allows the Powertrain Control Module (PCM) to accurately compensate for reference period variations. This enhances the ability of the PCM to detect misfire events over a wider range of engine speed and load conditions. The PCM stores the CKP system variation values after a learn procedure has been performed. If the PCM detects the CKP system variation values are not stored in the PCM memory, DTC P0315 sets.

Conditions For Running The DTC

1. DTCs P0335, P0336, P0341 and P1345 are not set.
2. The Engine Coolant Temperature (ECT) is more than 149° F (65° C).

Conditions For Setting The DTC

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

Action Taken When The DTC Sets

1. The control module illuminates the Malfunction Indicator Light (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 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 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 memory, 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 CKP sensor replacement.
5. Any engine repairs which disturb the CKP sensor relationship.

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

1. Worn crankshaft main bearings.
2. A damaged reluctor wheel.
3. Interference in the signal circuit of the CKP sensor.
4. A coolant temperature that is not within the Conditions For Running The DTC.
5. The ignition switch is in the ON position until the battery has sufficient voltage.
6. A PCM power disconnect with the ignition ON may erase the stored value and set DTC P0315.
7. Any foreign material passing between the CKP sensor and the reluctor wheel.

Scheme 169

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Knock Sensor (KS) produces an AC voltage at all engine speeds and loads. The Powertrain Control Module (PCM) then adjusts the spark timing based on the amplitude and frequency of the KS signal. The PCM uses the KS signal to calculate the average voltage range. The PCM checks the knock sensor and related wiring by comparing the actual knock signal to the calculated voltage range. If the PCM malfunctions in a manner that will not allow proper diagnosis of the KS system DTC P0325 sets.

The engine run time is more than 10 seconds. The ignition voltage is more than 10 volts.

The PCM detects a malfunction in the KS diagnostic circuitry that will not allow proper diagnosis of the KS system.

1. The control module illuminates the Malfunction Indicator Light (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 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. The knock sensor must be torqued correctly to 18 ft. lbs. (25 N.m).
2. The mounting between the sensor and the engine must be free of burrs, casting flash, and foreign material.
3. Verify that the knock sensor head is clear of hoses, brackets, and engine electrical wiring.

Scheme 170

DTC P0327: KNOCK SENSOR CIRCUIT - LOW VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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

1. DTCs P0116, P0117, P0118, P0121, P0122, P0123, P0125, P1114, P1115, P1121, or P1122 are not set.
2. The minimum noise level must be learned. The minimum noise level is learned when the following conditions are met: The Engine Coolant Temperature (ECT) must be more than 140° F (60° C). The engine RPM is between 475-975 for 10 seconds.
3. The Engine Coolant Temperature (ECT) is more than 140°F (60°C).
4. The engine run time is more than 10 seconds.
5. The Manifold Absolute Pressure (MAP) is less than 45 kPa.
6. The engine speed is between 1700-3000 RPM.
7. The system voltage is more than 10 volts.

The PCM detects that the KS signal is outside the calculated range or not present.

1. The control module illuminates the Malfunction Indicator Light (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 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. The knock sensor must be correctly tightened to 19 ft. lbs. (25 N.m).
2. The mounting between the sensor and the engine must be free of burrs, casting flash, and foreign material.
3. Ensure that the KS head is clear of hoses, brackets, and engine wiring.
4. For an intermittent condition, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 3 This step ensures that the KS is capable of detecting detonation and producing a signal.

Scheme 171

Scheme 172

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) used the Crankshaft Position (CKP) sensor to detect 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 no signal from the CKP sensor for more than 3 seconds, DTC P0335 sets.

1. DTCs P0101, P0102, P0103, or P0341 are not set.
2. The Camshaft Position (CMP) sensor is incrementing.
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 no signal from the CKP sensor for more than 3 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 following conditions may cause this DTC to set

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

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.

Scheme 173

Scheme 174

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) uses the Crankshaft Position (CKP) sensor to detect crankshaft speed and position. The CKP sensor connects to the PCM through the following circuits

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

If the PCM detects that the CKP sensor signal is incorrect for 3 seconds, DTC P0336 sets.

The engine is cranking or running.

The PCM determines that the CKP sensor signal is out of range for less than 3 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 following problems may cause this DTC to set

1. Crankshaft reluctor wheel damage or improper installation.
2. The sensor coming in contact with the reluctor wheel.
3. If the crankshaft rotates backwards, this DTC sets. This condition is only with vehicles equipped with a manual transmission. This condition can occur 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.

An improperly installed crankshaft could cause excess crankshaft end play.

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

Scheme 175

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Camshaft Position (CMP) sensor is a hall effect type sensor. The sensor produces one signal for each revolution of the camshaft in order to control the sequential fuel injection. The CMP sensor is designed to detect changes in a magnetic field. The Powertrain Control Module (PCM) supplies the CMP sensor with the following circuits

1. A 12-volt reference circuit.
2. A low reference circuit.
3. A signal circuit.

The CMP sensor produces a magnetic field whenever the ignition is ON. The CMP sensor is mounted near a reluctor wheel that is attached to the distributor shaft. When the distributor shaft rotates, and the reluctor wheel tooth passes by the CMP sensor, there is a change in the magnetic field. The CMP sensor converts each change in the magnetic field into a PULSE. If the PCM does not detect the CMP signal while the engine is running, Diagnostic Trouble Code (DTC) P0341 will set.

The engine is running.

The CMP sensor reference pulse is not detected once every 2 crankshaft revolutions.

1. The control module illuminates the Malfunction Indicator Light (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 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. Electromagnetic Interference (EMI) from the ignition coil or from the spark plug wires could cause a faulty signal condition in the CMP signal circuit to the PCM. Ensure that the routing of the CMP circuitry is correct.
2. If the condition is intermittent, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

1. 6 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 176

Scheme 177

DTC P0351: IGNITION CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The enhanced ignition system uses the Crankshaft Position (CKP) sensor in order to provide a timing input to the control module. Ignition Control (IC) spark timing for each cylinder is based on this input. The control module provides the ignition timing signal to the Ignition Control Module (ICM) to control the ignition coil. Each timing pulse detected by the ICM allows the ICM to energize the ignition coil. A large secondary ignition voltage is induced in the secondary coil by the primary coil. This high voltage is switched to the correct spark plug by the distributor. This Diagnostic Trouble Code (DTC) will set if the Powertrain Control Module (PCM) detects an unusually high or low voltage on the ignition timing signal circuit.

The engine is cranking.

The ignition control voltage is not 0.04-4.9 volts.

1. The control module illuminates the Malfunction Indicator Light (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 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 procedures.

1. 2 This step determines if the DTC is an intermittent.
2. 3 This step checks if the IC timing signal from the PCM is available at the ICM.

Scheme 178

Scheme 179

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

In order to maintain a reasonably low emissions of Hydrocarbons (HC), Carbon Monoxide (CO), and Oxides of Nitrogen (NOx), the engine controls system uses a three-way catalytic converter. The catalyst within the converter promotes a chemical reaction which oxidizes the HC and CO present in the exhaust gas. This reaction converts them into harmless water vapor and carbon dioxide. The catalyst also reduces NOx by converting the NOx to nitrogen. The Powertrain Control Module (PCM) monitors this process using Heated Oxygen Sensor (HO2S) bank 1 sensor 2. HO2S bank 1 sensor 2, located in the exhaust stream past the three-way catalytic converter, produces an output signal which indicates the oxygen storage capacity of the catalyst. This determines the catalyst's ability to convert exhaust emissions effectively. If the catalyst is functioning correctly, the HO2S bank 1 HO2S 2 signal will be far less active than that produced by HO2S bank 1 sensor 1. This indicates that the three-way catalytic converters oxygen storage capacity is operating at a threshold considered acceptable. When the conditions for running this DTC are met, the following occurs

1. The PCM captures the current rear HO2S rich or lean status.
2. The air/fuel ratio transitions from rich to lean or lean to rich depending on the capture rear HO2S rich or lean status.
3. The air/fuel ratio transitions a second time opposite the first air/fuel ratio transition.
4. The PCM captures the response time, the time the HO2S goes from below 300 mV to above 600 mV and from 600 mV to below 300 mV, of the front and rear HO2S when the air/fuel ratio transitions occurred.
5. The PCM measures the time it takes the rear HO2S voltage to cross a reference rich or lean threshold minus the time necessary for the front HO2S voltage to cross the same rich or lean threshold. The time difference from the front and rear HO2S is the oxygen storage capacity of the catalyst. This DTC sets if the time exceeds a predetermined threshold.

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0151, P0152, P0153, P0154, P0155, P0171, P0172, P0174, P0175, P0200, P0300, P0325, P0327, P0335, P0336, P0341, P0442, P0443, P0446, P0452, P0453, P0455, P0502, P0503, P0506, P0507, P1133, P1134, or P1153 are not set.
2. The Intake Air Temperature (IAT) is between 5-185° F (-15-85° C).
3. The Barometric Pressure (BARO) is more than 10.7 psi (74 kPa).
4. The engine is operating.
5. The Engine Coolant Temperature (ECT) is more than 158-248° F (70-120° C).
6. Since the end of the last idle period, the engine speed is more than 900 RPM for the one of thee following amounts of time: 40 Seconds For Manual Transmissions 45 Seconds 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 Light (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 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 procedures.

1. 3 This step inspects for conditions that can cause the 3-way catalytic converter efficiency to appear degraded.
2. 5 A catalytic converter which has been discolored may be due to an engine running rich, lean, or had a previous sever misfire. Verifying the fuel trim percentages may be of assistance in determining if such a condition exists.

Scheme 180

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 results in corresponding pressure changes in the fuel tank 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 P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0125, P0335, P0336, P0341, P0342, P0351, P0443, P0446, P0449, P0452, P0453, P0455, P0496, P0500, P0502, P0503, 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 86° F (30° C).
6. The start up IAT and ECT are within 15° F (8° C).
7. The Barometric (BARO) pressure 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 PCM will illuminate the Malfunction Indicator Light (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
2. The PCM will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

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, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__intermittent-conditions) under SELF DIAGNOSTIC SYSTEM.
2. To improve the visibility of the smoke exiting the EVAP system, observe the suspected leak area from different angles with J 41413-SPT.

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

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 181

Scheme 182

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

An ignition voltage is supplied directly to the Evaporative Emission (EVAP) 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 Light (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 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 procedures.

1. 2 This step tests if the concern is active. The Evaporative Emission (EVAP) purge solenoid is pules width module. You should hear a clicking sound when the purge solenoid is commanded to 50 percent. The clicking sound should stop when the EVAP purge solenoid is commanded to 0 percent. The rate at which the valve cycles should increase 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 solenoid.
3. 6 This step tests if a ground is constantly being applied to the EVAP purge solenoid.

Scheme 183

Scheme 184

DTC P0446: EVAP VENT SYSTEM BLOCKED OR RESTRICTED

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 open and the EVAP canister vent solenoid closed. 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 closed and the EVAP canister vent solenoid open. The control module monitors the Fuel Tank Pressure (FTP) sensor for a decrease in vacuum. If the vacuum does not decrease to near zero inches H2O in a calibrated time, this DTC sets.

1. DTCs P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0772, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, or P1120, 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 at least 30 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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.

An intermittent condition could be caused by a damaged EVAP vent housing, a temporary blockage at the EVAP vent valve inlet, or a pinched vent hose. A blockage in the vent system will also cause a poor fuel fill problem. To repair a blockage in the EVAP system, see EVAPORATIVE EMISSION SYSTEM CLEANING in REMOVAL & INSTALLATION article.

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

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

Scheme 185

Scheme 186

DTC P0449: EVAP CANISTER VENT SOLENOID VALVE CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

An ignition voltage is supplied to the Evaporative (EVAP) canister vent valve. The control module grounds the EVAP canister vent valve control circuit to close the valve by means of an internal switch called a driver. The scan tool displays the commanded 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 will illuminate the Malfunction Indicator Light (MIL) during the second consecutive trip in which the diagnostic test ran and failed.
2. The control module will store conditions which were present when the DTC set as Freeze Frame/Failure Records data.

1. The control module will turn OFF the MIL during the third consecutive trip in which the diagnostic ran and passed.
2. A current DTC, Last Test Failed, clears when the diagnostic runs and passes.
3. The History DTC will clear after 40 consecutive warm-up cycles without a malfunction.
4. The DTC can be cleared with a scan tool.

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

1. 2 Listen for a click when the valve operates. Verify that both the ON and 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 solenoid.
3. 6 This step tests if the EVAP vent solenoid control circuit is grounded.

Scheme 187

Scheme 188

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION 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 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 goes below a calibrated value, this DTC sets.

The following table illustrates the relationship between the FTP sensor signal voltage and the EVAP system pressure/vacuum. See RELATIONSHIP BETWEEN FTP SENSOR SIGNAL & EVAP SYSTEM PRESSURE/VOLTAGE .

RELATIONSHIP BETWEEN FTP SENSOR SIGNAL & EVAP SYSTEM PRESSURE/VOLTAGE

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 Light (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 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 number below refers to the step number in the diagnostic procedures.

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 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 189

Scheme 190

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION 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 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. See RELATIONSHIP BETWEEN FTP SENSOR SIGNAL & EVAP SYSTEM PRESSURE/VOLTAGE .

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 Light (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 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 number below refers to the step number in the diagnostic procedures.

1. 2 If DTC P0641 or P651 set, the 5-volt reference circuit maybe shorted to a voltage.

Scheme 191

Scheme 192

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 to rapidly, this DTC sets.

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

EVAP CANISTER PURGE/VENT VALVE OPERATION

1. DTC P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, and P1120 are not set
2. The engine is running.
3. The ignition voltage is between 10-18 volts.
4. The Barometric (BARO) pressure 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 (4-75° C).
7. 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 Light (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.

1. The 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. 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 any restriction in the EVAP system.
3. To improve the 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. For intermittent conditions, see «INTERMITTENT CONDITIONS»(/chevrolet/chevy-express-h2500/2003-2003/remont/testing-diagnostics/#engine-controls-self-diagnostics-43l__intermittent-conditions) under SELF-DIAGNOSTIC SYSTEM.

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

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 inches of H2O and 7 inches of H2O.

Scheme 193

Scheme 194

Scheme 195

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 Closed and the EVAP canister CLOSED. The control module monitors the Fuel Tank Pressure (FTP) sensor to determine if a vacuum is being drawn on the EVAP system. If the vacuum in the EVAP system is more than a predetermined value within a predetermined time, this DTC sets. See EVAP CANISTER PURGE/VENT VALVE OPERATION .

1. DTC P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0120, P0121, P0122, P0123, P0125, P0131, P0132, P0133, P0134, P0135, P0137, P0138, P0140, P0141, P0147, P0151, P0152, P0153, P0154, P0155, P0157, P0158, P0160, P0161, P0167, P0220, P0442, P0443, P0449, P0452, P0453, P0455, P0502, P0503, P1111, P1112, P1114, P1115, and P1120 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 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 Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails. WARNING: 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 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.

Scheme 196

DTC P0506: IDLE CONTROL SYSTEM - LOW RPM

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0171, P0172, P0174, P0175, P0200, P0300, P0442, P0443, P0446, P0449, P0455, P0496, P1111, P1112, P1114, P1115, P1121, P1122, P1380, and P1381 are not set.
2. The Engine Coolant Temperature (ECT) sensor is between 140-241°F (60-116°C).
3. The Barometric (BARO) pressure sensor is more than 65 kPa.
4. The engine run time is more than 60 seconds.
5. The Throttle Position (TP) sensor angle is less than 0.7 percent.
6. The Vehicle Speed Sensor (VSS) is less than 1 MPH.
7. The Ignition 1 Signal parameter is between 9-18 volts.
8. The Intake Air Temperature (IAT) sensor is more than 14°F (-10°C).
9. The above conditions are met for 2 seconds.

The actual engine speed is 100 RPM less than the desired engine speed for more than 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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.

Inspect for the following conditions

1. High resistance in an IAC circuit.
2. Restricted air intake system.
3. Proper operation and installation of all air intake components.
4. Collapsed, clogged, or loose air intake ducts.
5. A clogged air filter.
6. Proper operation of the Mass Air Flow (MAF) sensor, if equipped.
7. A tampered with or damaged throttle stop screw.
8. A tampered with or damaged throttle plate, throttle shaft, or throttle linkage.
9. Objects blocking the IAC passage or throttle bore.
10. Excessive deposits in the IAC passage or on the IAC pintle.
11. Excessive deposits in the throttle bore or on the throttle plate.
12. Vacuum leaks.
13. A low or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve.

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

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

1. 5 This test will determine the ability of the PCM and IAC valve circuits to control the IAC valve.
2. 7 This test will determine the ability of the PCM to provide the IAC valve control circuits with a ground. On a normal operating system, the test light should not flash while the IAC counts are incrementing.

Scheme 197

Scheme 198

Scheme 199

DTC P0507: IDLE CONTROL SYSTEM - HIGH RPM

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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

1. DTCs P0101, P0102, P0103, P0106, P0107, P0108, P0112, P0113, P0116, P0117, P0118, P0121, P0122, P0123, P0125, P0128, P0171, P0172, P0174, P0175, P0200, P0300, P0442, P0443, P0446, P0449, P0455, P0469, P1111, P1112, P1114, P1115, P1121, P1122, P1380, and P1381 are not set.
2. The Engine Coolant Temperature (ECT) sensor is between 140-241°F (60-116°C).
3. The Barometric (BARO) pressure sensor is more than 65 kPa.
4. The engine run time is more than 60 seconds.
5. The Throttle Position (TP) sensor angle is less than 0.7 percent.
6. The Vehicle Speed Sensor (VSS) is less than 1 MPH.
7. The ignition voltage is between 9-18 volts.
8. The Intake Air Temperature (IAT) sensor is more than 14°F (-10°C).
9. The above conditions are met for 2 seconds.

The actual engine speed is 200 RPM more than the desired engine speed for more than 5 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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.

Inspect for the following conditions

1. High resistance in an IAC valve control circuit.
2. The correct Positive Crankcase Ventilation (PCV) valve, properly installed and proper operation of the PCV valve.
3. Proper operation and installation of all air intake components.
4. Proper installation and operation of the Mass Air Flow (MAF) sensor, if equipped.
5. A tampered with or damaged throttle stop screw.
6. A tampered with or damaged throttle plate, throttle shaft, throttle linkage, or cruise control linkage, if equipped.
7. A skewed high TP sensor.
8. Excessive deposits in the IAC passage or on the IAC pintle.
9. Excessive deposits in the throttle bore or on the throttle plate.
10. Vacuum leaks.
11. A high or unstable idle condition could be caused by a non-IAC system problem that can not be overcome by the IAC valve.

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

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

1. 5 This test will determine the ability of the PCM and IAC valve circuits to control the IAC valve.
2. 7 This test will determine the ability of the PCM to provide the IAC valve control circuits with a ground. On a normally operating system, the test light should not flash while the IAC counts are incrementing.

Scheme 200

Scheme 201

Scheme 202

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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.

Information is not available from manufacturer.

Information is not available from manufacturer.

Information is not available from manufacturer.

Information is not available from manufacturer.

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

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

Scheme 203

DTC P0641: 5-VOLT REFERENCE CIRCUIT OUT-OF-RANGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

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

1. The Throttle Position (TP) sensor.
2. The Engine Oil Pressure (EOP) sensor.
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 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 met for more than 10 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 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 DTC with a scan tool.

1. 9 A short to voltage on the signal circuit of the Manifold Absolute Pressure (MAP) sensor will backfeed through the sensor into the 5-volt reference circuit and set this DTC.

Scheme 204

Scheme 205

DTC P0650: MIL CONTROL CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Malfunction Indicator Light (MIL) is located on the Instrument Panel Cluster (IPC). The MIL informs the driver that 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.

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

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

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

1. 5 This step tests for a short to ground in the MIL control circuit. With the PCM disconnected and the ignition ON the MIL should be OFF.
2. 6 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 206

Scheme 207

DTC P0651: SENSOR REFERENCE VOLTAGE CIRCUIT

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) provides 5 volts to the Fuel Tank Pressure (FTP) sensor. The PCM monitors the voltage on the 5 volt reference circuit. If the voltage is out of tolerance, DTC P0651 sets.

The engine must be running.

1. The PCM detects a voltage out of tolerance condition on the 5-volt reference circuit.
2. The above condition is met for more than 10 seconds.

1. The control module illuminates the Malfunction Indicator Light (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 DTC

1. The 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.

Scheme 208

Scheme 209

DTC P1106: MAP 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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 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 intermittently high, DTC P1106 sets.

1. The engine has been running for a length of time that is determined by start up coolant temperature. The length of time ranges from 5.5 minutes at less than -22° F (-30° C) to 10 seconds at more than 86° F (30° C).
2. DTC P0121, P0122, P0123 are not set.
3. The throttle angle is less than 1 percent when the engine speed is less than 1200 RPM.
4. The throttle angle is more than 12.5 percent when the engine speed is more than 1200 RPM.

The PCM detects that the MAP sensor voltage is intermittently 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 Light (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. 3 This step attempts to pinpoint the location of the intermittent fault.

Scheme 210

DTC P1107: MAP 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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 deceleration. The PCM should detect a high signal voltage at 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. The ignition is ON.
2. DTC P0121, P0122 and P0123 are not set.
3. The throttle angle is more than 0 percent when the engine speed is less than 800 RPM.
4. 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 intermittently less than 0.10 volts.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (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. 3 This step attempts to pinpoint the location of the intermittent fault.

Scheme 211

DTC P1111: IAT SENSOR CIRCUIT - INTERMITTENT HIGH SIGNAL VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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, P0116, P0117, P0118, P0125, P0128, P0502, P0503, P1114 and P1115 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 (-39°C) for more than 16 minutes.

1. The control module illuminates the Malfunction Indicator Light (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 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.

Scheme 212

DTC P1112: IAT SENSOR CIRCUIT - INTERMITTENT LOW SIGNAL VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 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.

1. The IAT is more than 262°F (128°C).
2. The condition exists for more than 16 minutes.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The control module illuminates the Malfunction Indicator Light (MIL) on the second consecutive ignition cycle that the diagnostic runs and fails.
3. 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.
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.

Scheme 213

DTC P1114: ECT SENSOR CIRCUIT - INTERMITTENT LOW SIGNAL VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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) for more than 16 minutes.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (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 214

DTC P1115: ECT SENSOR CIRCUIT - INTERMITTENT HIGH SIGNAL VOLTAGE

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article. If diagnosis 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 that the ECT sensor parameter is less than -36° F (-38° C) for more than 16 minutes.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (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 215

DTC P1121: TP SENSOR CIRCUIT - INTERMITTENT HIGH SIGNAL VOLTAGE

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

The Throttle Position (TP) sensor is used by the Powertrain Control Module (PCM) in order to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits

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

The PCM provides the TP sensor with the 5 volt reference circuit and a ground on the low reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from below 1.0 volt to greater than 4.0 volts through the TP sensor signal circuit. If the PCM detects an intermittent excessively high signal voltage, DTC P1121 sets.

1. The ignition is ON.
2. DTCs P0641 and P651 are not set.

The PCM detects that the TP sensor voltage is intermittently 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 Light (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. 7 This test will determine an intermittent faulty TP sensor utilizing the DMMs MIN MAX 100 millisecond capture mode.

Scheme 216

Scheme 217

DTC P1122: TP SENSOR CIRCUIT - INTERMITTENT LOW SIGNAL VOLTAGE

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

The Throttle Position (TP) sensor is used by the PCM in order to determine the throttle plate angle for various engine management systems. The TP sensor is a potentiometer type sensor with 3 circuits

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

The PCM provides the TP sensor with 5 volts on the 5-volt reference circuit. Rotation of the TP sensor rotor from the closed throttle position to the Wide Open Throttle (WOT) position provides the PCM with a signal voltage from less than 1 volt to more than 4 volts through the TP sensor signal circuit. If the PCM detects an intermittent excessively low signal voltage, this DTC will set.

1. The ignition is ON.
2. DTCs P0641 and P0651 are not set.

The PCM detects that the TP sensor voltage is intermittently less than 0.15 volt.

1. The control module stores the DTC information into memory when the diagnostic runs and fails.
2. The Malfunction Indicator Light (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. 6 This test will determine an intermittent faulty TP sensor utilizing the DMMs MIN MAX 100 millisecond capture mode.

Scheme 218

Scheme 219

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

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 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 he 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 of rich-to-lean and lean-to-rich transitions. A transitions defined as, the HO2S voltage changes from above 600 mV to below 200 mV or from below 200 mV to above 600 mV. If the PCM detects that the number of 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, P0121, P0122, P0123, P0131, P0132, P0134, P0135, P0151, P0152, P0154, P0155, P0200, P0300, P0442, P0446, P0452, P0453, P0455 or P0496 are not set.
2. The engine run time is more than 160 seconds.
3. The engine speed is between 1200-3000 RPM.
4. The Engine Coolant Temperature (ECT) sensor is more than 140°F (60°C).
5. The Mass Air Flow (MAF) sensor is between 18-55 g/s.
6. The loop status is Closed.
7. The Throttle Position (TP) sensor is more than 5 percent.
8. The fuel tank level remaining is more than 10 percent.
9. The ignition 1 signal voltage is between 10-18 volts.
10. The Evaporative Emissions (EVAP) purge solenoid command is more than 1 percent.
11. The above conditions are met for 100 seconds.

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

1. The control module illuminates the Malfunction Indicator Light (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 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 non-emission related diagnostic.
4. Clear the DTC with a scan tool.

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

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

Scheme 220

Scheme 221

DTC P1258: ENGINE OVER-TEMPERATURE CONDITION

Note. To locate components, see COMPONENT LOCATIONS . For circuit reference, see WIRING DIAGRAMS . For connector terminal identification, see CONNECTOR IDENTIFICATION . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) used the Engine Coolant Temperature (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 2 groups of 4 cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the PCM is able to reduce the temperature of the coolant.

The engine is running.

The engine coolant temperature is above 270°F (132°C) 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 2 groups of 4 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 passes.
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 222

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. 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 rotation 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, P0121, P0122, P0123, 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 Light (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 223

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 . If an intermittent condition exists, see INTERMITTENT CONDITIONS under SELF-DIAGNOSTIC SYSTEM. If testing requires component removal or replacement, see appropriate REMOVAL & INSTALLATION article.

The Powertrain Control Module (PCM) detects engine misfire by detecting variations in crankshaft deceleration between firing strokes. For accurate detection of engine misfire, the PCM must distinguish between crankshaft deceleration caused by actual misfire and deceleration caused by rough road conditions. The Anti-Lock Brake System (ABS) can detect if the vehicle is on a rough road based on wheel acceleration or deceleration data supplied by the wheel speed sensors. If the ABS detects rough road above a predetermined threshold, this information is sent to the PCM via serial data. The PCM can then take the rough road into account when calculating misfire. Even if the ABS is malfunctioning and cannot detect rough roads, the misfire diagnostic will continue to run. However, if a misfire Diagnostic Trouble Code (DTC) sets, this additional DTC also sets indicating that rough road data was not available during the misfire calculation due to a serial data malfunction.

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 Light (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 procedures.

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

Scheme 224

CHEVY EXPRESS - G1500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

CHEVY EXPRESS - G2500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SAVANA - G1500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

SAVANA - G2500

See ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

See also:
• NO-START DIAGNOSIS
• TROUBLE SHOOTING - NO CODES - 4.3L CHEVY EXPRESS & SAVANA
• SYMPTOMS
• SYSTEM & COMPONENT TESTING - 4.3L CHEVY EXPRESS & SAVANA
• COOLING SYSTEM TROUBLE SHOOTING
• SENSOR OPERATING RANGE CHARTS - TRUCKS
• BASIC DIAGNOSTIC PROCEDURES - 4.3L CHEVY EXPRESS & SAVANA
• DIAGNOSTIC STARTING POINT - ENGINE CONTROLS
• DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS
• VEHICLE DATA RECORDER
• POWERTRAIN CONTROL MODULE
• DIAGNOSTIC TROUBLE CODE DEFINITIONS
• DTC P0336: CRANKSHAFT POSITION SENSOR CIRCUIT PERFORMANCE
• DTC P0315
• P0420 & P0430
• P0442
• P0446
• P0133 or P0153
• P0140 or P0160
• P1133 or P1153
• P0135, P0141, P0155 or P0161
• P0016
• P0101
• P0102
• P0103
• P0106
• P0107
• P0108
• P0112
• P0113
• P0116
• P0117
• P0118
• P0121
• P0122
• P0123
• P0125
• P0128
• P0131
• P0132
• P0134
• P0137
• P0138
• P0171
• P0172
• P0200
• P0230
• P0300
• P0325
• P0327
• P0335
• P0341
• P0351
• P0443
• P0449
• P0452
• P0453
• P0455
• P0496
• P0506
• P0507
• P0601 - P0607
• P0641
• P0650
• P0651
• P1106
• P1107
• P1111
• P1112
• P1114
• P1115
• P1121
• P1122
• P1258
• P1380
• P1381
• CODE TYPES
• INTERMITTENT CONDITIONS