LEMON Manuals: Even more car manuals for everyone
Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 81 (Engine Controls - Self-Diagnostics - 8.1L) >> Diagnostic Tests >> DTC P0342: CMP Signal Low >> Diagnostic Procedures

Diagnostic Procedures

WARNING: This page does not describe the selected car, but rather 13 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Sierra, 2002 GMC Savana Special, 2002 GMC Savana Camper Special, and 2002 GMC Savana. However, it is still accessible from the selected car via links, so may be relevant.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM.
  2. Connect a scan tool. Start the engine. Monitor the CMP signal high-to-low and low-to-high transition parameter in the Engine Data List 1 using the scan tool. Does the scan tool parameter increment? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records Data for this DTC. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC, or as close to the Freeze Frame/Failure Records data that you observed. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Turn OFF the ignition. Disconnect the CMP sensor. Turn ON the ignition, with the engine OFF. Use a Digital Multimeter (DMM) connected to battery ground in order to measure the voltage on the 12-volt reference circuit. Is the voltage near battery voltage? If yes, go to next step. If no, go to step  7.
  5. Use the DMM in order to measure the voltage from the 12-volt reference voltage circuit of the CMP sensor to the CMP sensor low reference circuit. Is the voltage near battery voltage? If yes, go to next step. If no, go to step  9.
  6. Start the engine. Use the scan tool in order to monitor the CMP signal high-to-low and low-to-high transition. Use a test lamp connected to battery voltage to momentarily and repeatedly probe the signal circuit. Does the CMP signal high-to-low and low-to-high transition counters increment when the test lamp contacts the signal circuit? If yes, go to step  15. If no, go to step  10.
  7. Turn OFF the ignition. Disconnect the PCM connector C2 located on the opposite side of the manufacturers logo. Use the DMM in order to measure the resistance of the CMP 12-volt reference circuit. Is the resistance 0-5 ohms? If yes, go to next step. If no, go to step  12.
  8. Test the CMP 12-volt reference circuit for the following:
    • A grounded circuit.
    • A poor connection.

    Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.

  9. Turn OFF the ignition. Disconnect the PCM connector C1 located on the same side as the manufacturers logo. Use a DMM in order to measure the resistance of the CMP low reference circuit. Is the resistance 0-5 ohms? If yes, go to step  16. If no, go to step  13.
  10. Turn OFF the ignition. Disconnect the PCM connector C1 located on the same side as the manufacturers logo. Use the DMM in order to measure the resistance of the CMP signal circuit. Is the resistance 0-5 ohms? If yes, go to next step. If no, go to step  14.
  11. Turn ON the ignition, with the engine OFF. Test the CMP signal circuit for the following:
    • A grounded circuit.
    • A circuit shorted to a voltage.

    Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.

  12. Inspect the CMP 12-volt reference circuit for an open. If you find an open, repair the circuit. Did you find and correct the condition? If yes, go to step  19. If no, go to step  16.
  13. Repair an open in the CMP low reference circuit. After repairs, go to step  19.
  14. Repair an open in the CMP signal circuit. After repairs, go to step  19.
  15. Inspect for poor connections at the CMP harness connector. If you find a poor connection, repair the connector as necessary. Did you find and correct the condition? If yes, go to step  19. If no, go to step  17.
  16. Inspect the PCM harness connector for poor connections. If you find a poor connection, repair the connector as necessary. Did you find and correct the condition? If yes, go to step  19. If no, go to step  18.
  17. Replace the CMP sensor. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. After repairs, go to step  19.
  18. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  19. Clear the DTCs with a scan tool. Turn OFF the ignition for 30 seconds. Start the engine. Operate the vehicle within the Conditions for Running DTC. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  20. Observe the stored information, Capture Info with a scan tool. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
scientia non olet · About LEMON Manuals