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Home >> Buick >> 2002 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 3.1L Engine >> System Tests >> Mil Inoperative >> Diagnostic Procedures
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Diagnostic Procedures

  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 engine. Does engine start? If yes, go to next step. If no, go to step  9.
  3. Inspect the fuse supplying voltage to the MIL. Is fuse open? If yes, go to step  7. If no, go to next step.
  4. Turn ignition off. Disconnect the PCM connector containing the MIL control circuit. Turn ignition on, with engine off. Probe 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.
  5. Turn ignition off. Remove IPC. Probe the MIL ignition positive voltage circuit at IPC harness connector with a test light connected to a good ground. See WIRING DIAGRAMS article. Is test light illuminated? If yes, go to next step. If no, go to step  8.
  6. Test the MIL control circuit for an open or high resistance and repair as necessary. Did you find and correct the condition? If yes, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS . If no, go to step  14.
  7. Repair the short to ground in the MIL ignition positive voltage circuit. After repairs, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  8. Repair the open in the MIL ignition positive voltage circuit. After repairs, DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  9. Inspect the PCM fuse and the ignition 1 main fuse. Is one or both of the fuses open? If yes, go to step  12. If no, go to next step.
  10. Turn ignition off. Disconnect the PCM. Turn ignition on, with engine off. Connect a test light between the PCM ignition positive voltage circuits and a good ground. Does the test light illuminate while probing ALL PCM ignition positive voltage circuits? If yes, go to next step. If no, go to step  12.
  11. Connect test light from PCM battery positive voltage circuit and good ground. Does the test light illuminate? If yes, go to step  13. If no, go to next step.
  12. Locate and repair the open or short to ground in the PCM ignition feed circuits or the PCM battery positive voltage circuit. After repairs, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  13. Inspect for a poor PCM ground or a poor PCM ground connection. Did you find and correct the condition? If yes, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS . If no, go to step  15.
  14. Inspect for poor connections at the IPC and repair as necessary. Did you find and correct the condition? If yes, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS . 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 DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS . If no, go to step  17.
  16. Replace the IPC. After repairs, DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
  17. Replace PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article. Perform PCM relearn procedure. See POWERTRAIN CONTROL MODULE  under PROGRAMMING. After repairs, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS .
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