Diagnostic Trouble Code (DTC) Charts: P0645

WARNING: This page does not describe the selected car, but rather 30 other vehicles, including the 2004 Mercury Sable, 2004 Mercury Mountaineer, 2004 Mercury Monterey, 2004 Mercury Marauder, and 2004 Mercury Grand Marquis. However, it is still accessible from the selected car via links, so may be relevant.

P0645

Description:	Monitors the wide open throttle A/C cutoff (WAC) circuit output from the PCM. The test fails if: When the PCM grounds the WAC circuit, excessive current draw is detected on the WAC circuit; or, with the WAC circuit not grounded by the PCM, voltage is not detected on the WAC circuit (the PCM expects to detect VPWR voltage coming through the WAC relay coil to the WAC circuit).
Possible Causes:	Open or shorted WAC circuit. Damaged WAC relay (or CCRM). Open VPWR circuit to the WAC relay. Damaged PCM.
Diagnostic Aids:	The A/CCR control circuit can be monitored using the WACF & WAC PID. When the WACF PID reads YES, a fault is currently present. An open circuit or short to ground can only be detected when the PCM is not grounding the circuit. A short to power can only be detected when the PCM is grounding the circuit. During the KOEO and KOER self-test, the WAC circuit is cycled on and off. Verify the A/C and defrost were off during the KOEO and KOER self-tests. Check the ACCS PID to verify. If the vehicle is not equipped with A/C, DTC P1460 can be ignored.
Application	Key On Engine Off	Key On Engine Running	Continuous Memory
Mustang	GO to X: Constant Control Relay Module (CCRM) STEP 49	GO to X: Constant Control Relay Module (CCRM) STEP 49	GO to X: Constant Control Relay Module (CCRM) STEP 59
All Others	GO to KM: Air conditioning clutch relay circuit STEP 1	GO to KM: Air conditioning clutch relay circuit STEP 1	GO to KM: Air conditioning clutch relay circuit STEP 14