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Home >> Pontiac >> 2002 >> Firebird Formula, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 5.7L >> Diagnostic Tests >> DTC P0650: Mil Control Circuit >> Diagnostic Procedures
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Diagnostic Procedures

  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 panel (IP) is operational. If the IP is completely inoperative, see appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Verify whether the MIL turns ON and OFF when commanded. Turn ON the ignition, with the engine OFF. Command the MIL ON and OFF using the scan tool. Repeat the commands as necessary. Does the MIL turn ON and OFF when commanded? 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 observe. Does the DTC fail this ignition cycle? If yes, go to next step. If no, see DIAGNOSTIC AIDS .
  4. Inspect the fuse that supplies battery voltage to the MIL. Is the fuse open? If yes, go to step  10. If no, go to next step.
  5. Turn OFF the ignition. Disconnect the PCM. Turn ON the ignition. Is the MIL OFF? If yes, go to next step. If no, go to step  11.
  6. Turn OFF the ignition. Remove the fuse that supplies voltage to the MIL. Turn ON the ignition, with the engine OFF. Connect a Digital Multimeter (DMM) from the MIL control circuit to a good ground. Is the voltage 0 V? If yes, go to next step. If no, go to step  12.
  7. Turn OFF the ignition. Reinstall the fuse that supplies voltage to the MIL. Turn ON the ignition, with the engine OFF. Probe the MIL control circuit in the PCM harness connector with a fused jumper wire connected to ground. Is the MIL ON? If yes, go to step  15. If no, go to next step.
  8. Turn OFF the ignition. Remove the IP. Probe the MIL battery voltage circuit at the IP harness connector with a test lamp connected to a good ground. Is the test lamp illuminated? If yes, go to next step. If no, go to step  13.
  9. Test the MIL control circuit for an open or high resistance and repair as necessary. Did you find and correct a condition? If yes, go to step  18. If no, go to step  14.
  10. Repair the short to ground in the battery positive voltage circuit. After repairs, go to step  18.
  11. Repair the short to ground in the MIL control circuit. After repairs, go to step  18.
  12. Repair the short to voltage in the MIL control circuit. After repairs, go to step  18.
  13. Repair the open in the MIL battery positive voltage. After repairs, go to step  18.
  14. Inspect for poor connections at the IP and repair as necessary. Did you find and correct the condition? If yes, go to step  18. If no, go to step  16.
  15. Inspect for poor connections at the PCM and repair as necessary. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  16. Replace the IP. See appropriate ANALOG INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. After repairs, go to step  18.
  17. Replace the PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Reprogram PCM. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to next step.
  18. 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.
  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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