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Diagnostic Procedure

WARNING: This page is about a different car, the 2002 Buick Regal and 2002 Buick Century. However, it is still accessible from the selected car via links, so may be relevant.
  1. If diagnostic system check was not performed, go to DIAGNOSTIC SYSTEM CHECK  under SELF-DIAGNOSTICS SYSTEM. If diagnostic system check was performed, go to next step.
  2. Turn ignition on. Use scan tool to command A/C relay ON and OFF in Special Functions, Engine Output Controls list. If A/C relay turns on and off with each command, check connection with A/C relay and relay socket. If A/C relay does not turn on and off with each command, go to next step.
  3. Turn ignition off. Remove A/C clutch relay. Turn ignition on. Using a test light connected to ground, probe voltage supply terminal of A/C clutch relay. If test light illuminates, go to next step. If test light does not illuminate, go to step  10.
  4. Connect a test light between voltage supply side and control circuit side of A/C clutch relay. Use scan tool to command A/C relay ON and OFF. If test light turns on and off with each command, go to step  8. If test light does not turn on and off with each command, go to next step.
  5. If test light illuminates regardless of command by scan tool, go to step  7. If test light does not illuminate regardless of command by scan tool, go to next step.
  6. Check A/C compressor clutch relay control circuit of A/C compressor clutch relay for a short to voltage or an open. See WIRING DIAGRAMS . If a short to voltage or an open condition exists, repair as necessary. When repair is complete, go to step  13. If short to voltage or an open condition is not found, go to step  9.
  7. Check A/C compressor clutch relay control circuit of A/C compressor clutch relay for a short to ground. See WIRING DIAGRAMS . If a short to ground exists, repair as necessary. When repair is complete, go to step  13. If short to ground is not found, go to step  9.
  8. Check A/C compressor clutch relay harness connector for poor connections. If poor connection is found, repair as necessary. When repair is complete, go to step  13. If poor connection is not found, go to step  11.
  9. Check PCM harness connector for poor connections. If poor connection is found, repair as necessary. When repair is complete, go to step  13. If poor connection is not found, go to step  12.
  10. Repair A/C compressor clutch relay battery positive voltage circuit. When repair is complete, go to step  13.
  11. Replace A/C compressor clutch relay. See COMPRESSOR RELAY  under REMOVAL & INSTALLATION. When repair is complete, go to step  13.
  12. Replace PCM. See POWERTRAIN CONTROL MODULE under COMPUTERIZED ENGINE CONTROLS in REMOVAL, OVERHAUL & INSTALLATION - CENTURY, GRAND PRIX, IMPALA, MONTE CARLO & REGAL article in ENGINE PERFORMANCE. When repair is complete, go to next step.
  13. Use scan tool to clear DTCs. See CLEARING DIAGNOSTIC TROUBLE CODES . Turn ignition on. Turn A/C system on and allow to operate for at least 30 seconds. If any DTCs are set, go to step 2. If no DTCs are set, system is okay
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