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HOMESERVICE MANUALSCHEVROLET2003TRAILBLAZER 4.2 S, 4WDREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 364 (ENGINE CONTROLS SELF-DIAGNOSTICS)DIAGNOSTIC TESTSDTC P0650: MIL CONTROL CIRCUITDIAGNOSTIC PROCEDURES
2003 Chevrolet TrailBlazer 4.2 S, 4WD

Diagnostic Procedures

2003 Chevrolet TrailBlazer 4.2 S, 4WDSECTION Diagnostic Procedures
WARNING: This page is about a different car, the 2003 Pontiac Aztek and 2003 Buick Rendezvous. 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. Verify whether the instrument cluster is operational. If instrument panel is completely inoperative, diagnose instrument cluster. Refer to appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Command the MIL ON and OFF with scan tool. Does the MIL turn ON and OFF when commanded with a scan tool? If yes, go to next step. If no, go to step  4.
  3. Observe the Freeze Frame/Failure Records for this DTC. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running the DTC. See CONDITIONS FOR RUNNING DTC . 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, problem is intermittent. Refer to INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 3.4L AZTEK & RENDEZVOUS article.
  4. Inspect the fuse that supplies ignition voltage to the MIL. Is the fuse open? If yes, go to step  12. If no, go to next step.
  5. Turn ignition off. Disconnect the PCM. Turn ignition on. Is the MIL OFF? If yes, go to next step. If no, go to step  13.
  6. Turn ignition off. Remove the fuse that supplies voltage to the MIL. Turn ignition on, with engine off. Measure the voltage from the MIL control circuit to a good ground. Is the voltage less than 0.3 volt? If yes, go to next step. If no, go to step  14.
  7. Turn ignition off. Install the fuse that supplies voltage to the MIL. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the MIL control circuit of the PCM and a good ground. Is the MIL illuminated? If yes, go to step  11. If no, go to next step.
  8. Turn ignition off. Remove the instrument panel cluster. Probe the MIL battery positive voltage circuit of the IPC harness connector with a test light that is connected to a good ground. Does the test light illuminate? If yes, go to next step. If no, go to step  15.
  9. Test the MIL control circuit for an open or high resistance. Did you find and correct a condition? If yes, go to step  18. If no, go to next step.
  10. Test for an intermittent and for a poor connection at the IPC. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  11. Test for an intermittent and for a poor connection at the PCM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  12. Repair short to ground in the battery positive voltage circuit. After repairs, go to step  18.
  13. Repair short to ground in the MIL control circuit. After repairs, go to step  18.
  14. Repair short to voltage in the MIL control circuit. After repairs, go to step  18.
  15. Repair open in the MIL ignition voltage circuit. After repairs, go to step  18.
  16. Replace the IPC. After replacing instrument panel, go to step  18.
  17. Replace PCM. See REMOVAL & INSTALLATION - AZTEC & RENDEZVOUS article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  18. Clear the DTCs with a scan tool. Turn ignition off for 30 seconds. Start engine. Operate the vehicle within the Conditions for Running DTC. See CONDITIONS FOR RUNNING DTC . Does the DTC run and pass? If yes, go to next step. If no, go to step  2.
  19. 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.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.