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Home >> Cadillac >> 2003 >> Seville SLS >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Self-Diagnostics >> System Tests >> Malfunction Indicator Lamp Inoperative >> 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 Cluster (IPC) is operational. If 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, see INTERMITTENT CONDITIONS  under SELF-DIAGNOSTIC SYSTEM. If no, go to next step.
  3. Inspect the fuse that supplies ignition voltage to the cluster. Is the fuse open? If yes, go to step  10. If no, go to next step.
  4. Turn ignition off. Remove the fuse that supplies ignition voltage to the cluster. Disconnect the PCM. Turn ignition on, with engine off. Measure voltage between the MIL control circuit in the PCM harness connector and a good ground. Is the voltage less than 0.3 volts? If yes, go to next step. If no, go to step  11.
  5. Turn ignition off. Install the fuse that supplies ignition voltage to the cluster. Turn ignition on, with engine off. Connect a 3-amp fused jumper wire between the MIL control circuit in the PCM harness connector and a good ground. Is the MIL illuminated? If yes, go to step  9. If no, go to next step.
  6. Turn ignition off. Remove the IPC. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Turn engine on, with engine off. Probe the ignition 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  12.
  7. Test the MIL control circuit for an open or high resistance. Did you find and correct a condition? If yes, go to step  15. If no, go to next step.
  8. Test for an intermittent and/or poor connections at the IPC. Did you find and correct the condition? If yes, go to step  15. If no, go to step  13.
  9. Test for an intermittent and/or poor connections at the PCM. Did you find and correct the condition? If yes, go to step  15. If no, go to step  14.
  10. Repair the short to ground in the ignition voltage circuit. Did you complete the repair? If yes, go to step. 15.
  11. Repair the short to voltage in the MIL control circuit. Did you complete the repair? If yes, go to step  15.
  12. Repair the open in the ignition voltage circuit. Did you complete the repair? If yes, go to step  15.
  13. Replace the IPC. See appropriate INSTRUMENT PANELS article in ACCESSORIES & EQUIPMENT. Did you complete the replacement? If yes, go to step  15.
  14. 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.
  15. Turn off the ignition for 30 seconds. Start the engine. Does the MIL operate correctly? If yes, go to next step. If no, go to step  2.
  16. 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.
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