HVAC
GENERAL DESCRIPTION
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
DTC DESCRIPTION
PCM monitors voltage through A/C compressor relay. Checking voltage every 10 sec. under detecting condition, if the voltage higher than the specified value is detected for more than 5 sec., PCM sets P0647.
DTC DETECTING CONDITION
SPECIFICATION
SCHEMATIC DIAGRAM
MONITOR DTC STATUS
1. Check DTC Status
(1) Connect scantool to Data Link Connector(DLC).
(2) IG "ON".
(3) Select "Diagnostic Trouble Codes(DTCs)" mode, and then Press F5(INFO) to check DTC's information from the DTCs menu
(4) Read "DTC Status" parameter.
(5) Is "Present" Fault displayed?
YES
> Go to "Terminal and connector inspection" procedure.
NO
> Fault is intermittent caused by poor contact in the sensor's and/or PCM's connector or was repaired and PCM memory was not cleared. Thoroughly check connectors for looseness, poor connection, ending, corrosion, contamination, deterioration, or damage. Repair or replace as necessary and go to "Verification of Vehicle Repair" procedure.
TERMINAL AND CONNECTOR INSPECTION
1. Many malfunctions in the electrical system are caused by poor harness and terminal condition. 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 CIRCUIT INSPECTION
1. Check voltage
(1) IG "OFF".
(2) Disconnect A/C relay.
(3) IG "ON" and ENG "OFF".
(4) Measure the voltage between terminal 30 of A/C relay harness connector and chassis ground.
(5) Measure the voltage between terminal 85 of A/C relay harness connector and chassis ground.
Specification : B+
(6) Is the measured voltage normal?
YES
> Go to "Control circuit inspection" procedure.
NO
> Check the fuse between Battery and A/C relay.
> Check Chassis ground for looseness.
> Repair open or short to ground in power harness and go to "Verification of Vehicle Repair" procedure.
CONTROL CIRCUIT INSPECTION
1. Check short in harness
(1) IG "ON".
(2) Disconnect A/C relay.
(3) Measure the voltage between terminal 86 of A/C relay harness connector and chassis ground.
Specification : Approx. 0V
(4) Is the measured voltage within specification ?
YES
> Go to "Component inspection" procedure.
NO
> Repair Short in Coil control harness and go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Check A/C relay
(1) IG "OFF".
(2) Disconnect A/C relay.
(3) Measure the resistance between terminal 30 and 87 of A/C relay.
(4) Measure the resistance between terminal 85 and 86 of A/C relay.
SPECIFICATION
(5) Is the measured resistance within specification ?
YES
> Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "Verification of Vehicle Repair" procedure.
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.
NOTE:
There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM. After testing PCM on the vehicle, use this function before reusing the PCM
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. Press F5(INFO) and confirm that "DTC Readiness Flag" indicates "Complete". If not, drive the vehicle within conditions noted in the freeze frame data or enable conditions
3. Read "DTC Status" parameter
4. Is "History (Not Present)" fault displayed?
YES
> System performing to specification at this time. Clear the DTC
NO
> Go to the applicable troubleshooting procedure.