P0646
P0646Component Location:
General Description
The A/C relay is activated if the A/C switch is ON while the blower is running and system operation is enabled the PCM. 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 PCM also inhibits compressor operation on starting to permit running conditions to stabilize.
DTC Description
If there is Short to ground in A/C control relay control circuit, PCM sets DTC P0646.
DTC Detecting Condition:
Schematic Diagram:
Monitor Scantool Data
1. Connect scantool to Data Link Connector (DLC).
2. Warm up the engine to normal operating temperature.
3. Monitor "A/C Relay" parameters on scantool.
4. Are the parameters displayed correctly?
YES - Fault is intermittent caused by poor contact in the sensor's and/or ECM's connector or was repaired and ECM memory was not cleared. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of vehicle Repair" procedure.
NO - Go to "Inspection & Repair" procedure.
Terminal and Connector Inspection
1. Many malfunctions in the electrical system are caused by poor harness and terminals. Faults can also be caused by interference from other electrical systems, and mechanical or chemical damage.
2. Thoroughly check connectors for looseness, poor connection, bending, corrosion, contamination,deterioration, or damage.
3. Has a problem been found?
YES - Repair as necessary and go to "Verification of vehicle Repair" procedure
NO - Go to "Power circuit inspection" procedure.
Power Supply Circuit Inspection
1. Check Voltage of power circuit from battery
1. IG "OFF".
2. Disconnect A/C Relay.
3. IG "ON".
4. Measure the voltage between terminal 3 of A/C Relay harness connector and ground.
Specification : B +
5. Is the measured voltage within specification?
YES - Go to "Control circuit inspection" procedure.
NO
- Check "10 A SNSR" fuse between a main relay and a A/C relay.
- Check Open or Short to ground in power circuit of A/C relay and then go to "Verification of vehicle Repair" procedure.
Control Circuit Inspection
1. IG "OFF".
2. Disconnect A/C Relay.
3. IG "ON".
4. Measure the voltage between terminal 5 of A/C relay and ground.
Specification : Approx. 11 V
5. Is the measured voltage within specification?
YES - Go to "Component inspection" procedure.
NO - Repair Short to ground in A/C relay control circuit and then go to "Verification of Vehicle Repair" procedure.
Component Inspection
1. A/C relay check
1. Key "OFF".
2. Disconnect A/C relay.
3. Measure the resistance between terminal 1 and 2 of A/C relay component side.
4. Measure the resistance between terminal 3 and 5 of A/C relay component side.
Specification :
5. Is the measured resistance within specifications?
YES - Substitute with a known - good ECM and check for proper operation. If the problem is corrected, replace ECM and go to "Verification of Vehicle Repair" procedure.
NOTE: There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others
NO - Substitute with a known - good A/C relay and check for proper operation. If the problem is corrected, replace A/C relay and go to "Verification of Vehicle Repair" procedure.
Verification of Vehicle Repair
After a repair, it is essential to verify that the fault has been corrected.
1. Connect scan tool and select "Diagnostic Trouble Codes (DTCs)" mode.
2. Clear the DTCs and Operate the vehicle within DTC Enable conditions in General information.
3. Are any DTCs present?
YES - Go to the applicable troubleshooting procedure.
NO - System is performing to specification at this time.