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Home >> Chevrolet >> 2002 >> Blazer 4D Utility, 4WD, Part Time >> Repair and Diagnosis >> External Pages >> Different car >> Section 379 (Engine Controls Self-Diagnostics - 3.4L) >> Diagnostic Tests >> DTC P1374: 3X Reference Circuit >> Diagnostic Procedure

Diagnostic Procedure

WARNING: This page is about a different car, the 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, 2003 Chevrolet Monte Carlo, and 2003 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
  1. Perform diagnostic system check - engine controls. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS  under SELF-DIAGNOSTIC SYSTEM. After performing diagnostic system check - engine controls, go to next step.
  2. Attempt to start the engine. Does the engine start and run? If yes, go to step  4. If no, go to next step.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition switch to OFF position for 30 seconds. Start the engine. Operate the vehicle within the Conditions For Running. See CONDITIONS FOR RUNNING . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC fail this ignition? If yes, go to next step. If no, go to DIAGNOSTIC AIDS .
  4. Turn ignition switch to OFF position. Disconnect Ignition Control Module (ICM) harness connector. Remove the injector fuse. Turn ignition switch to RUN position, engine OFF. Momentarily probe the low resolution engine speed signal circuit at the ICM harness connector using a test light connected to battery voltage. Observe the ENGINE SPEED parameter using a scan tool. Is an engine speed displayed? If yes, go to step  8. If no, go to next step.
  5. Did the test light illuminate? If yes, go to step  7. If no, go to next step.
  6. Turn ignition switch to OFF position. Disconnect the PCM harness connectors. Turn ignition switch to RUN position, engine OFF. Check the ICM low resolution engine speed signal circuit for the following conditions:
    • An open.
    • A short to voltage.
    • High resistance.

    Did you find and correct the condition? If yes, go to step  12. If no, go to step  9.

  7. Turn ignition switch to OFF position. Disconnect the PCM harness connectors. Check the low resolution engine speed signal circuit of the ICM for a short to ground or high resistance. Did you find and correct the condition? If yes, go to step  12. If no, go to step  9.
  8. Check for an intermittent and for a poor connection at the ICM. Did you find and correct the condition? If yes, go to step  12. If no, go to step  10.
  9. Check for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  12. If no, go to step  11.
  10. Replace the ICM. After repair, go to step  12.
  11. Replace PCM. See POWERTRAIN CONTROL MODULE in appropriate REMOVAL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After replacing PCM, go to next step.
  12. Using a scan tool, clear the DTCs. Turn ignition switch to OFF position. Start the engine. Operate the vehicle within the Conditions For Running. See CONDITIONS FOR RUNNING . You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  13. Using the scan tool, observe the stored information in CAPTURE INFO. Does the scan tool display any DTCs that you have not diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay at this time.
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