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HOMESERVICE MANUALSBUICK1999REGAL LSREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - INTRODUCTIONSELF-DIAGNOSTIC SYSTEMDLC DIAGNOSIS OR NO SCAN TOOL DATA3.0L
1999 Buick Regal LS

DLC Diagnosis Or No Scan Tool Data: 3.0L

1999 Buick Regal LSSECTION 3.0L
NOTE: Perform On-Board Diagnostic (OBD) system check after completing any repairs. 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. Install scan tool. Turn ignition on, with engine off. If scan tool powers up, go to next step. If scan tool does not power up, go to step  8.
  3. Attempt to start engine. If engine starts and continues to run, go to step  11. If engine does not start, or starts and then stalls, go to next step.
  4. Turn ignition off. Disconnect ECM harness connectors. Turn ignition on. Using a test light connected to ground, probe ignition feed circuit at ECM 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  6.
  5. Using a test light connected to battery positive, probe ground circuits at ECM harness connector. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates for all ground circuits, go to step  15. If test light does not illuminate for all ground circuits, go to step  7.
  6. Repair ignition feed circuit.
  7. Repair short to ground in affected circuit.
  8. Disconnect scan tool. Using a test light connected to chassis ground, probe battery feed circuit at DLC. 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  10.
  9. Using a test light connected to battery positive, probe both ground circuits at DLC. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates for both ground circuits, go to step  17. If test light does not illuminate for both ground circuits, go to step  13.
  10. Repair battery feed circuit to DLC.
  11. Disconnect scan tool. Using a test light connected to battery positive, probe DLC ground circuits. See appropriate wiring diagram in WIRING DIAGRAMS article. If test light illuminates for both ground circuits, go to next step. If test light does not illuminate for both ground circuits, go to step  13.
  12. Check for open, short to ground or short to voltage in serial data circuit. Repair as necessary. If circuit is okay, go to step  14.
  13. Repair open or high resistance in DLC ground circuits.
  14. Connect scan tool to another vehicle and check for proper operation. If scan tool operates properly, go to next step. If scan tool does not operate properly, go to step  17.
  15. Check ECM for proper terminal tension or poor connections. Repair as necessary. If terminals and connections are okay, go to next step.
  16. Replace ECM. Perform ECM relearn procedures.
  17. Replace faulty scan tool.
RENDER: 1.0x

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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.