DTC P0645: A/C CLUTCH RELAY CIRCUIT

Monitor & Set Conditions

A/C clutch relay may also be referred to as A/C compressor clutch relay. A/C clutch relay circuit is monitored when ignition is on and battery voltage is greater than 10.4 volts. DTC may be stored if an open or short exists in A/C clutch relay control circuit.

Possible Causes

• Intermittent Condition
• Fused Ignition Switch Output Circuit Open
• A/C Clutch Relay
• A/C Clutch Relay Control Circuit Short To Ground
• A/C Clutch Relay Control Circuit Open
• PCM

Testing

1. Turn ignition on with engine off. Using DRBIII(R) scan tool, actuate A/C clutch relay. Listen for clicking sound at A/C clutch relay. The A/C clutch relay is located in Power Distribution Center (PDC) at driver's side front corner of engine compartment. If clicking sound is heard at A/C clutch relay, go to next step. If clicking sound is not heard at A/C clutch relay, go to step 3 .

2. Start engine and run at operating temperature. Using scan tool, monitor data parameters related to the DTC while wiggling system related wiring harness. Watch for parameter values to change and/or a DTC to set. Using scan tool, read FREEZE FRAME data. Road test vehicle under conditions displayed in FREEZE FRAME data parameters. Using scan tool, actuate A/C clutch relay and wiggle wiring harness. Turn ignition off. Visually inspect PCM connectors for corroded, pushed out or damaged terminals. Inspect wiring harness and connectors between A/C compressor and PCM for chafed, pierced or partially broken wires. If a problem is found, repair as necessary. If no problem is found, check for any Technical Service Bulletins (TSB) that may apply.

3. Remove A/C clutch relay from PDC. Visually inspect A/C clutch relay connector terminals in PDC for corroded, pushed out or damaged terminals. Repair as necessary. Turn ignition on with engine off. Using DVOM connected to ground, measure voltage at Pink/Dark Blue wire terminal (A/C clutch relay fused ignition switch input) in PDC for A/C clutch relay. If voltage is greater than 10 volts, go to next step. If voltage is 10 volts or less, repair open or short to ground in A/C clutch relay fused ignition switch input circuit.

4. Using DVOM, measure resistance between A/C clutch relay terminals No. 1 (85) and No. 2 (86). If A/C clutch relay resistance is 50-90 ohms, go to next step. If A/C clutch relay resistance is not 50-90 ohms, replace A/C clutch relay.

5. Ensure ignition is off and A/C clutch relay is removed. Disconnect PCM harness connectors. PCM is located at passenger's side rear corner of engine compartment. Using DVOM, measure resistance between ground and terminal No. 1 (Dark Blue/Orange wire) at PCM harness connector C3. If resistance is 100 ohms or greater, go to next step. If resistance is less than 100 ohms, repair short to ground in Dark Blue/Orange wire between PCM and A/C clutch relay.

6. Using DVOM, measure resistance of Dark Blue/Orange wire between terminal No. 1 at PCM harness connector C3 and terminal No. 85 in PDC. If resistance is less than 5 ohms, go to next step. If resistance is 5 ohms or greater, repair open in Dark Blue/Orange wire between PCM and PDC.

7. Replace and program PCM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.