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Engine Controls Self-Diagnostics - 4.3L: Other GMC Savana H2500

Testing & Diagnostics ~4005 words

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 .

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.

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»(ref-158087-S06555639282003091100000) 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.

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.

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.

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»(ref-158087-S41901059152003091100000) .
  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»(ref-158087-S35484044562003091200000) . If any other DTCs set, refer to «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-158087-S41901059152003091100000) 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 .

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.

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.

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.

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.

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.

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