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DTC P0645: A/C Clutch Relay Circuit: Testing

  1. Turn ignition on, engine not running. With the DRBIII®, actuate the A/C Clutch Relay. Is the A/C Clutch Relay clicking? Relay is located in Power Distribution Center (PDC). If yes, go to next step. If no, go to step  3.
    2. WARNING: When the engine is operating, do not stand in a direct line with the fan. Do not put your hands near the pulleys, belts or fan. Do not wear loose clothing.
  2. The conditions that set the DTC are not present at this time. The following may help in identifying the intermittent condition. With the engine running at normal operating temperature, monitor the DRBIII® parameters related to the DTC while wiggling the wiring harness. Look for parameter values to change and/or a DTC to set. Review the DRBIII® Freeze Frame information. If possible, try to duplicate the conditions under which the DTC was set. Refer to any Technical Service Bulletins (TSB) that may apply. Visually inspect the related wire harness. Look for any chafed, pierced, pinched, or partially broken wires. Visually inspect the related wire harness connectors. Look for broken, bent, pushed out, or corroded terminals. Were any of the above conditions present? If yes, repair as necessary. If no, test is complete.
  3. Turn the ignition off. Remove A/C clutch relay from the PDC. Turn ignition on, engine not running. Measure the Fused Ignition Switch Output circuit voltage at the A/C clutch relay harness connector in the PDC. Is the voltage above 10.0 volts? If yes, go to next step. If no, repair the open/short to ground in the Fused Ignition Switch Output circuit. Check the related fuse.
  4. Turn ignition off. Measure the resistance between terminals No. 1 (85) and 2 (86) at the A/C Clutch Relay (component side). Is the resistance between 50.0 and 90.0 ohms? If yes, go to next step. If no, replace the A/C Clutch Relay.
  5. Ensure ignition is off. Disconnect PCM connectors. Check connectors and clean/repair as necessary. Measure the A/C Clutch Control circuit resistance between ground and the A/C Clutch Relay Control circuit at the PCM harness connector. Is the resistance below 100 ohms? If yes, repair the A/C Clutch Relay Control circuit for a short to ground. If no, go to next step.
  6. Measure the resistance of the A/C Clutch Relay Control circuit from the A/C Clutch Relay harness connector to the PCM harness connector. Is the resistance below 5.0 ohms? If yes, go to next step. If no, repair open in A/C Clutch Relay Control circuit.
  7. There are no possible causes remaining, replace PCM. Program the new PCM. See PROGRAMMING .
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