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 PCM. When A/C is requested, the Engine Control Module(PCM) 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 PCM delays grounding the relay circuit for a short time, so the PCM can adjust the engine idle speed for the additional load. The PCM 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
PCM sets DTC P0646 if the PCM detects signal lower than the possible range of a properly operating sensor.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Electrical Check | 1. Open or short to ground in power circuit 2. Open or short to ground in Control circuit 3. Poor connection or damaged harness 4. Faulty A/C Compressor Relay |
Enable Conditions |
•
10V< Battery voltage <16V | |
Threshold Value |
•
Short to Ground or Line Break | |
Diagnostic Time |
•
50 sec. | |
Mil On Condition |
•
- |
