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HOMESERVICE MANUALSBUICK1999REGAL LSREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - INTRODUCTIONSELF-DIAGNOSTIC SYSTEMMIL INOPERATIVE2.2L & 2.4L
1999 Buick Regal LS

2.2L & 2.4L

1999 Buick Regal LSSECTION 2.2L & 2.4L
  1. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK . After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. If MIL is illuminated, go to next step. If MIL is not illuminated, go to step  4.
  3. Check for poor connections at battery feed circuit and ignition positive voltage 2 circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22. If circuits are okay, go to step  5.
  4. Attempt to start engine. If engine starts, go to step  6. If engine does not start, go to step  7.
  5. Check for poor PCM ground connections at PCM and engine block. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22.
  6. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a test light connected to ground, probe MIL control circuit at PCM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If MIL illuminates, go to step  8. If MIL does not illuminate, go to step  9.
  7. Check ignition and battery feed fuses. If fuses are okay, go to step  10. If fuses are open, go to step  11.
  8. Check for poor battery feed, ignition positive voltage 2 or MIL control circuit connections. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22. If circuits are okay, go to step  12.
  9. If test light illuminates, go to step  13. If test light does not illuminate, go to step  14.
  10. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a test light connected to ground, probe ignition positive voltage 2 circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step  15. If test light does not illuminate, go to step  16.
  11. Check for short to ground in fuse circuit that was open. Repair as necessary and replace fuse. After repairs, go to step  22.
  12. Replace PCM. Perform PCM relearn procedures. After repairs, go to step  22.
  13. Repair short to voltage in MIL control circuit. After repairs, go to step  22.
  14. Check for open or poor connection in MIL control circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22. If circuit is okay, go to step  17.
  15. Using a test light connected to ground, probe PCM battery positive feed circuit at PCM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates, go to step  18. If test light does not illuminate, go to step  19.
  16. Repair open in ignition positive voltage 2 circuit. After repairs, go to step  22.
  17. Check for open in battery positive or ignition positive voltage 2 circuits. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. After repairs, go to step  22. If circuits are okay, go to step  20.
  18. Check for poor connections at battery positive voltage or ignition positive voltage 2 circuit. Repair as necessary. After repairs, go to step  22. If circuits are okay, go to step  21.
  19. Repair open in PCM battery positive voltage circuit. After repairs, go to step  22.
  20. Replace Instrument Panel Cluster (IPC). After IPC replacement, go to step  22.
  21. Check for poor PCM ground connections at PCM and engine block. Repair as necessary. After repairs, go to next step. If connections are okay, go to step  12.
  22. Start engine and allow it to reach normal operating temperature. Using scan tool, check for DTCs. If DTCs are present, diagnose DTCs. See DIAGNOSTIC TESTS in appropriate TESTS W/CODES article. If DTCs are not present, system is okay.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.