P0645-A/C CLUTCH RELAY CIRCUIT

For a complete wiring diagram Refer to Section 8W.

When Monitored:
With the ignition on. Battery voltage greater than 10 volts. A/C Switch on.
Set Condition:
An open or shorted condition is detected in the A/C clutch relay control circuit. One Trip Fault. Three good trips to turn off the MIL.

Possible Causes

(F942) FUSED IGNITION SWITCH OUTPUT CIRCUIT

(A917) FUSED B+ CIRCUIT

(C13) A/C CLUTCH RELAY CONTROL CIRCUIT OPEN

(C13) A/C CLUTCH RELAY CONTROL CIRCUIT SHORTED TO GROUND

A/C CLUTCH RELAY

PCM

Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. (Refer to 9 - ENGINE - DIAGNOSIS AND TESTING).

Diagnostic Test

1.A/C CLUTCH RELAY OPERATION

Is the A/C Clutch Relay operating?

Yes

Refer to the INTERMITTENT CONDITION Diagnostic Procedure.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 2

2.A/C CLUTCH RELAY RESISTANCE

Is the resistance between 60 to 80 ohms?

Yes

Go To 3

Replace the A/C Clutch Relay.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

3.(F942) FUSED IGNITION SWITCH OUTPUT CIRCUIT

Does the test light illuminate brightly?

Yes

Go To 4

Repair the open or short to ground in the (F942) Fused Ignition Switch Output circuit. Check and replace any open fuses.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

4.(A917) FUSED B+ CIRCUIT

Does the test light illuminate brightly?

Yes

Go To 5

Repair the open or short to ground in the (A917) Fused B+ circuit. Check and replace any open fuses.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

5.(C13) A/C CLUTCH RELAY CONTROL CIRCUIT OPEN

CAUTION: Do not probe the PCM harness connectors. Probing the PCM harness connectors will damage the PCM terminals resulting in poor terminal to pin connection. Install Miller Special Tool #8815 to perform diagnosis.

Is the resistance below 5.0 ohms?

Yes

Go To 6

Repair the open in the (C13) A/C Clutch Relay Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

6.(C13) A/C CLUTCH RELAY CONTROL CIRCUIT SHORTED TO GROUND

Is the resistance below 5.0 ohms?

Yes

Repair the short to ground in the (C13) A/C Relay Clutch Control circuit.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Go To 7

7.PCM

NOTE: Before continuing, check the PCM harness connector terminals for corrosion, damage, or terminal push out. Repair as necessary.

Were there any problems found?

Yes

Repair as necessary.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)

Replace and program the Powertrain Control Module per Service Information.
Perform the POWERTRAIN VERIFICATION TEST. (Refer to 9 - ENGINE - STANDARD PROCEDURE)