The A/C clutch relay is activated if the A/C switch is operated while the blower is running and system operation is enabled by the ECM. When A/C is requested, the Engine Control Module(ECM) provides a ground path to the A/C clutch relay control circuit. When the relay circuit is grounded, the A/C clutch relay is energized. The ECM delays grounding the relay circuit for a short time, so the ECM can adjust the engine idle speed for the additional load. The ECM will temporarily de-energized the A/C clutch relay for one or more of the following conditions:
-Full acceleration when the throttle is at WOT.(Wide Open Throttle)
-Risk of overheating: Engine coolant temp. exceeds threshold value
-A/C system pressure exceeds threshold value
-Engine starting
If there is Short to ground in A/C control relay control circuit, PCM sets DTC P0646.
Item | Detecting Condition | Possible cause |
DTC Strategy |
•
Circuit check, low |
•
Poor connection
•
Open or short to ground in A/C relay circuit
•
Faulty ECM |
Enable Conditions |
•
- | |
Threshold value |
•
Short circuit to GND | |
Diagnosis Time |
•
Continuous | |
MIL On Condition |
•
NO MIL |
