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HOMESERVICE MANUALSBUICK1999REGAL LSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - INTRODUCTIONSELF-DIAGNOSTIC SYSTEMMIL INOPERATIVE3.1L & 3.4L
1999 Buick Regal LS

3.1L & 3.4L

1999 Buick Regal LSSECTION 3.1L & 3.4L
NOTE: After any repairs are completed, perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK .
  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. 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 fuse is open, go to step  15.
  4. Turn ignition on. Using a test light connected to ground, backprobe ignition feed circuit at instrument cluster harness connector . See appropriate wiring diagram in WIRING DIAGRAMS 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 harness connectors. Turn ignition on. Using a fused jumper wire, jumper MIL driver circuit at PCM harness connector to ground. See appropriate wiring diagram in WIRING DIAGRAMS 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 open, go to step  14.
  7. Turn ignition off. Disconnect PCM harness connectors. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit at PCM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS 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 battery feed circuit at PCM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS 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. If ground and ground connection are okay, go to next step.
  10. Check for poor PCM harness connection. Repair as necessary. If connection is okay, go to step  16.
  11. Check for open in MIL driver circuit. See appropriate wiring diagram in WIRING DIAGRAMS article. Repair as necessary. If circuit is okay, go to step  17.
  12. Repair open in ignition feed circuit to instrument cluster. Repair as necessary.
  13. Locate and repair open in PCM battery feed circuit or PCM ignition feed circuit. Repair as necessary.
  14. Locate and repair short to ground in PCM battery feed circuit or PCM ignition feed circuit. Repair as necessary.
  15. Locate and repair short to ground in instrument cluster ignition feed circuit. Repair as necessary.
  16. Replace PCM. Perform PCM relearn procedures.
  17. Check MIL driver circuit for poor connection at instrument cluster. Repair as necessary. If connection is okay, diagnose instrument cluster.
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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.