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Home >> Buick >> 1998 >> Century Custom >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Tests W/Codes - 3.1L Engine >> Self-Diagnostic System >> Mil Inoperative
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Mil Inoperative

  1. Perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK , then go to next step.
  2. Attempt to start engine. If engine starts, go to next step. If engine does not start, go to step 6).
  3. Check instrument cluster ignition feed fuse. If fuse is okay, go to next step. If fuses are blown, go to step 15).
  4. Turn ignition on. Using a test light connected to ground, probe instrument cluster connector ignition feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 12).
  5. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using a jumper wire connected to ground, jumper PCM connector MIL driver circuit. See WIRING DIAGRAMS - 3.1L article. If MIL illuminates, go to step 10). If MIL does not illuminate, go to step 11).
  6. Check PCM ignition feed and battery feed fuses. If fuses are okay, go to next step. If fuses are blown, go to step 14).
  7. Turn ignition off. Disconnect PCM connector. Turn ignition on. Using a test light connected to ground, probe PCM connector ignition feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
  8. Using a test light connected to ground, probe PCM connector battery feed circuit. See WIRING DIAGRAMS - 3.1L article. If test light illuminates, go to next step. If test light does not illuminate, go to step 13).
  9. Check for poor PCM ground or PCM ground connection. Repair as necessary. After repairs, perform OBD system check. If ground and ground connection are okay, go to next step.
  10. Check for poor PCM connection. Repair as necessary. After repairs, perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If connection is okay, go to step 16).
  11. Check for open in MIL driver circuit. See WIRING DIAGRAMS - 3.1L article. Repair as necessary. After repairs, perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If circuit is okay, go to step 17).
  12. Repair open in instrument cluster ignition feed circuit. Repair as necessary. After repairs, perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
  13. Locate and repair open in PCM battery feed circuit or PCM ignition feed circuit. Repair as necessary. After repairs, perform OBD system check.
  14. Locate and repair short to ground in PCM battery feed circuit or PCM ignition feed circuit. Repair as necessary. After repairs, perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
  15. Locate and repair short to ground in instrument cluster ignition feed circuit. Repair as necessary. After repairs, perform OBD system check.
  16. Replace PCM. Perform PCM relearn procedures. After repairs, perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
  17. Check for poor instrument cluster MIL driver circuit connection. Repair as necessary. After repairs, perform POWERTRAIN ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . If connection is okay, diagnose instrument cluster.
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