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Engine Control System - Self-Diagnostics - 4.2L: Other Chevrolet TrailBlazer I

Testing & Diagnostics ~3462 words

Code Types

There are 4 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 will illuminate SERVICE light.
  4. Type "D" - Non-emissions related. Does not illuminate MIL or 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 (If Equipped) 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 (If Equipped) Monitors secondary air operation.

Hard Failures

Hard failures cause Malfunction Indicator Light (MIL) to illuminate and remain on until problem is repaired. If light comes on and remains on (light may flash) during vehicle operation, cause of malfunction must be determined using DTC charts. If a sensor fails, PCM will use a substitute value in its calculations to continue engine operation. In this condition, commonly known as limp-in mode, the vehicle runs but driveability will not be optimum.

Intermittent Failures

Intermittent failures may cause Malfunction Indicator Light (MIL) to flicker or illuminate and go out after the intermittent fault goes away. However, the corresponding trouble code will be retained in PCM memory. If related fault does not reoccur within a certain time frame, related trouble code will be erased from PCM memory. Intermittent failures may be caused by a sensor, connector or wiring related problems. See INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article.

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.

CRANKSHAFT POSITION SENSOR

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

  1. Install scan tool.
  2. Using scan tool, monitor the PCM for DTCs. If other DTCs are set, except DTC P1336, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-155898-S19906497452003062800000) .
  3. With scan tool, select the crankshaft position variation learn procedure.
  4. Observe the fuel cut-off for the engine that you are performing the learn procedure on.
  5. The scan tool instructs you to perform the following: Block drive wheels. Apply parking brake. Cycle ignition from OFF to ON. Apply and hold brake pedal. Start and idle engine. Turn OFF the A/C. Place transmission in Park (A/T) or Neutral (M/T). The scan tool monitors certain component signals to determine if all the conditions are met to continue with the procedure. The scan tool only displays the condition that inhibits the procedure. The scan tool monitors the following components: Crankshaft Position (CKP) sensor activity. If there is a CKP sensor condition, refer to the applicable DTC that set. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-155898-S19906497452003062800000) . Camshaft Position (CMP) sensor activity. If there is a CMP sensor condition, refer to the applicable DTC that set. See «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-155898-S19906497452003062800000) . Engine Coolant Temperature (ECT). If engine coolant temperature is not warm enough, idle the engine until engine coolant temperature reaches correct temperature.
  6. With scan tool, enable the crankshaft position system variation learn procedure.
  7. Slowly increase the engine speed to the RPM that you observed.
  8. Immediately release the throttle when fuel cut-off is reached.
  9. The scan tool displays Learn Status: Learned this ignition. If scan tool does NOT display this message and no additional DTCs set, see «DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS»(ref-155898-S30062612662003062800000) under SELF-DIAGNOSTIC SYSTEM. If a DTC set, see «DIAGNOSTIC TROUBLE CODE DEFINITIONS»(ref-155898-S19906497452003062800000) .
  10. Turn ignition off 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® terminal. Procedure uses a Tech 2™ 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.

Remote Programming

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

Programming Verification

  1. Turn ignition off for 30 seconds.
  2. Start engine.

Pass-Thru Procedure

Pass-Thru programming allows 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 procedure.

Note. The TIS supports service programming with the Tech 2™ scan tool only.

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

Off-Board Remote Procedure

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 scan tool.

Note. Ensure Tech 2™ scan tool and terminal are both equipped with the latest software before performing programming.

  1. Obtain the Vehicle Identification Number (VIN) of the vehicle for which the module is being programmed.
  2. Launch the TIS application at the terminal.
  3. Select the Service Programming System.
  4. Highlight the following information on the Select Diagnostic Tool and Programming Process screen: Select Diagnostic Tool-Select Tech 2™ scan tool. Select Programming Process. Identify whether an existing module is being reprogrammed or replaced with a new one. Select ECU location. Select Off-Board Programming Adapter.
  5. Select Next.
  6. Follow the directions on the Preparing for Communication screen for connecting the following components: The control module. The Off-Board Programming Adapter (OBPA). Refer to TIS Users Guide for a listing of the OBPA. Tech 2™ scan tool.
  7. Select the Service Programming Request Information function on the Tech 2™.
  8. Follow the Tech 2 instructions to obtain the module data and security information.
  9. After the Tech 2™ has received the data from the module, exit the Request Info mode.
  10. Disconnect the Tech 2™ from the OBPA.
  11. Turn OFF the Tech 2™.
  12. Connect the Tech 2™ to the terminal.
  13. Turn ON the Tech 2™.
  14. Select Next at the terminal after the Tech 2™ 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 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™.
  29. Disconnect the Tech 2™ from the terminal.
  30. Connect the Tech 2™ to the OBPA.
  31. Turn ON the Tech 2™.
  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™.
  41. Disconnect the OBPA from the Tech 2™ and the control module.

Off-Board Pass-Thru Procedure

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 scan tool.

Note. Ensure Tech 2™ scan tool and terminal are both equipped with the latest software before performing programming.

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

THEFT DETERRENT LEARN PROCEDURE

There are 2 available methods to perform the programming procedure

  1. The 10-minute procedure which requires a Tech 2™ and a Techline® terminal.
  2. The 30-minute procedure which does not require the use of any tools.

10-Minute Learn Procedure

Note. Tools required are Tech 2™ scan tool and Techline® terminal with current Service Programming System (SPS) software.

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

30-Minute Learn Procedure

  1. Turn ignition on, with engine off.
  2. Attempt to start engine, then release the key to ON (vehicle will not start).
  3. Observe the SECURITY telltale, after about 10 minutes the telltale will turn OFF.
  4. Turn ignition off and wait 5 seconds.
  5. Repeat steps 1 - 4 two more times for a total of 3 cycles/30 minutes (the vehicle is now ready to relearn the Passlock™ Sensor Data Code and/or passwords on the next ignition switch transition from OFF to CRANK).
  6. Start engine (vehicle has now learned the Passlock™ Sensor Data Code and/or password).
  7. With 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 4 heated oxygen sensors, all 4 heater circuits have been diagnosed. The I/M System Status will indicate NO under the Completed column when any of the required tests for that system have not run. The following is a list of conditions that would set the I/M System Status indicator to NO

  1. Vehicle is new from the factory and has not yet been driven through the necessary drive conditions to complete the tests.
  2. Battery has been disconnected or discharged below operating voltage.
  3. Control module power or ground has been interrupted.
  4. Control module has been reprogrammed.
  5. 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, proceed to SYMPTOMS or INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 4.2L BRAVADA, ENVOY, ENVOY XL, TRAILBLAZER & TRAILBLAZER EXT article for diagnosis by symptom (i.e., ROUGH IDLE, NO-START, etc.) or intermittent diagnostic procedures.

MALFUNCTION INDICATOR LIGHT INOPERATIVE

Note. For circuit reference, see WIRING DIAGRAMS .

MALFUNCTION INDICATOR LIGHT ALWAYS ON

Note. For circuit reference, see WIRING DIAGRAMS .

BRAVADA

For wiring diagrams, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

ENVOY & ENVOY XL

For wiring diagrams, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

TRAILBLAZER & TRAILBLAZER EXT

For wiring diagrams, see ENGINE PERFORMANCE in SYSTEM WIRING DIAGRAMS article in ELECTRICAL.

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