The A/C relay is activated if the A/C switch is ON while the blower is running and system operation is enabled the ECM. Power is then supplied to the A/C compressor electromagnetic clutch and A/C system is operated. The A/C compressor is switched out to prevent it running when full engine output is required or there is a risk of overheating.The ECM also inhibits compressor operation on starting to permit running conditions to stabilize.
If there is Short to ground in A/C Relay circuit, ECM sets DTC P0646.
Item | Detecting Condition | Possible Cause |
DTC Strategy |
•
Circuit check, low | 1. Poor connection 2. A/C Relay 3. Short to ground in A/C compressor circuit 4. Faulty ECM |
Enable Conditions |
•
- | |
Threshold Value |
•
Short circuit to GND | |
Diagnostic Time |
•
Continuous | |
MIL ON Condition |
•
NO MIL |
