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Home >> Pontiac >> 2000 >> 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. Perform On-Board Diagnostic (OBD) system check. See ON-BOARD DIAGNOSTIC (OBD) SYSTEM CHECK  under SELF-DIAGNOSTIC SYSTEM. After performing OBD system check, go to next step.
  2. Turn ignition on, with engine off. Using scan tool, command relay on and off. If relay responds as commanded, go to next step. If relay does not respond as commanded, go to step  5.
  3. Turn ignition off. Disconnect PCM harness connector C2. Turn ignition on. Using DVOM set on 10-amp scale, measure current between ground and relay control circuit at PCM harness connector for 2 minutes. If current draw is less than 0.75 amp, see DIAGNOSTIC AIDS . If current draw is not less than 0.75 amp, go to next step.
  4. Turn ignition off. Disconnect relay. Check resistance between ground and relay control circuit at PCM harness connector. If resistance is infinite, go to step  12. If resistance is not infinite, go to step  10.
  5. Turn ignition off. Disconnect relay. Connect test light between relay control circuit and relay ignition feed circuit at underhood electrical center. Turn ignition on, with engine off. 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.
  6. Using a test light connected to ground, probe relay ignition feed circuits at underhood electrical center. If test light illuminates for each circuit, go to next step. If test light does not illuminate for each circuit, go to step  11.
  7. Turn ignition off. Reconnect relay. Disconnect PCM harness connector C2. Turn ignition on. Connect a fused jumper wire between ground and relay control circuit at PCM harness connector. If relay operates, go to step  9. If relay does not operate, go to step  10.
  8. Check for faulty relay connections. Repair as necessary. After repairs, go to step  14. If connections are okay, go to step  12.
  9. Check for faulty PCM harness connections. Repair as necessary. After repairs, go to step  14. If connections are okay, go to step  13.
  10. Repair faulty relay control circuit. After repairs, go to step  14.
  11. Repair faulty relay ignition feed circuit. After repairs, go to step  14.
  12. Replace relay. After replacing relay, go to step  14.
  13. Replace PCM. Program replacement PCM using required equipment. After replacing PCM, go to next step.
  14. 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 scan tool indicates that this test ran and passed, go to next step. If scan tool does not indicate that this test ran and passed, go to step  2.
  15. Using scan tool, select CAPTURE INFO, REVIEW INFO function. If any undiagnosed DTCs are displayed, go to applicable DTC test. If no undiagnosed DTCs are displayed, system is okay.
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