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Home >> Pontiac >> 2001 >> Firebird Formula, Automatic >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Self-Diagnostics - 5.7L >> Diagnostic Tests >> DTC P0645: A/C Clutch Relay Control Circuit >> Diagnostic Procedures

Diagnostic Procedures

  1. If HVAC diagnostic system check was performed, go to next step. If HVAC diagnostic system check was not performed, go to HVAC DIAGNOSTIC SYSTEM CHECK  under DIAGNOSTIC SYSTEM CHECKS. After performing HVAC diagnostic system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command A/C relay on and off. If relay responds as commanded, go to next step. If relay does not respond as commanded, go to DIAGNOSTIC AIDS .
  3. Turn ignition off. Locate and remove A/C compressor clutch relay located in bottom underhood fuse block. See Figure and Figure . Using a test light connected to ground, probe A/C compressor clutch relay connector terminal D10 (Pink wire). Turn ignition on. If test light illuminates for each circuit, go to next step. If test light does not illuminate for each circuit, go to step  10.
  4. Connect test light between A/C compressor clutch relay connector terminal C8 (Dark green/White wire) and D10 (Pink wire). Turn ignition on. Using scan tool, command 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 remains illuminated with each command, go to step  7. If test light does not remain illuminated with each command, go to next step.
  6. Check for open or short to voltage in Dark Green/White wire between A/C compressor clutch relay connector terminal C8 and PCM connector C2 terminal No. 43. See Figure. Repair as necessary. After repairs, go to step  13. If circuit is okay, go to step  9.
  7. Check for short to ground in Dark Green/White wire between A/C compressor clutch relay connector terminal C8 and PCM connector C2 terminal No. 43. See Figure. Repair as necessary. After repairs, go to step  13. If circuit is okay, go to step  9.
  8. Check for poor connections at A/C compressor clutch relay. Repair as necessary. After repairs, go to step  13. If connections are okay, go to step  11.
  9. Check for poor connections at PCM. Repair as necessary. After repairs, go to step  13. If connections are okay, go to step  12.
  10. Repair faulty Pink wire between A/C compressor clutch relay and A/C CRUISE fuse (15-amp) located in bottom underhood fuse block. After repairs, go to step  13.
  11. Replace A/C compressor clutch relay. After repairs, go to step  13.
  12. Replace PCM. See REMOVAL, OVERHAUL & INSTALLATION - CARS article. After replacing PCM, go to next step.
  13. Using scan tool, clear DTCs. Start and warm engine to normal operating temperature. Select DTC, SPECIFIC, then enter this DTC. Operate vehicle within conditions for setting this DTC. If DTC resets, go to step  2. If DTC does not reset, system is okay.
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