LEMON Manuals: Even more car manuals for everyone: 1960-2025
Home >> Cadillac >> 2003 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> Diagnostic Tests >> DTC P0650: Mil Control Circuit >> Diagnostic Procedures
April 5, 2026: LEMON Manuals is launched! Read the announcement.

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 Cluster (IPC) is operational. If the IPC is completely inoperative, see appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Command the MIL on and off with a 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 off the ignition for 30 seconds. Start the engine. Operate the vehicle within the 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 cycle? If yes, go to next step. If no, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM.
  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 Powertrain Control Module (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 ignition 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 volts? If yes, go to next step. If no, go to step  14.
  7. Turn ignition off. Install the fuse that supplies ignition voltage to the MIL. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the PCM MIL control circuit 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 IPC. Turn ignition on, with engine off. Probe the MIL ignition voltage circuit of the IPC harness connector with a test light 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/or poor connections 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/or poor connections at the PCM. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  12. Repair the short to ground in the ignition voltage circuit. Did you complete the repair? If yes, go to step  18.
  13. Repair the short to ground in the MIL control circuit. Did you complete the repair? If yes, go to step  18.
  14. Repair the short to voltage in the MIL control circuit. Did you complete the repair? If yes, go to step  18.
  15. Repair the open in the MIL ignition voltage circuit. Did you complete the repair? If yes, go to step  18.
  16. Replace the IPC. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Did you complete the replacement? If yes, go to step  18.
  17. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL & INSTALLATION - DEVILLE & SEVILLE article. Did you complete the replacement? If yes, go to next step.
  18. Clear the DTCs with a scan tool. Turn off the ignition for 30 seconds. Start the engine and operate vehicle within the Conditions For Running DTC. You may also operate vehicle within the conditions that you observed from the Freeze Frame/Failure Records. Did the DTC fail this ignition cycle? If yes, go to step  2. If no, go to next step.
  19. Observe the Capture Info with a scan tool. Are there any DTCs that have not been diagnosed? If yes, see DIAGNOSTIC TROUBLE CODE DEFINITIONS . If no, system is okay.
scientia non olet · About LEMON Manuals