P0685
DTC P0685 ECM/PCM POWER RELAY CONTROL CIRCUIT / OPENComponent Location:
GENERAL DESCRIPTION
The PCM provides ground to one side of the coil of the main relay and the other side is connected to the battery. The PCM monitors battery voltage and the voltage after the main relay.
DTC DESCRIPTION
Checking the controlling state of main relay every 10 sec. under detecting condition, if open or short in the circuit is detected for more than 5 sec., PCM sets P0685.
DTC DETECTING CONDITION
DTC Detecting Condition:
* If Main relay has a fault (ex. Open) under engine running, the DTCs,P0638/P0685/P1295/P21 06, can happen at the same time.
P0638 Throttle Actuator Control Range/Performance (Bank 1)
P0685 PCM/PCM Power Relay Control Circuit 10 pen
P1295 Throttle Actuator Control System - Power Management
P2106 Throttle Actuator Control System - Forced Limited Power
Specification:
Schematic Diagram:
MONITOR SCANTOOL DATA
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 F4(DTAL) to check DTC's information from the DTCs menu
4. Read "DTC Status" parameter.
5. Is parameter displayed "Present fault"?
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 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 CIRCUIT INSPECTION
1. IG "OFF"
2. Disconnect Main Relay
3. IG "ON" & ENG "OFF".
4. Measure voltage between harness terminal 2 of Main Relay and chassis ground.
5. Measure voltage between harness terminal 5 of Main Relay and chassis ground.
Specification : B+
6. Is the measured voltage within specification?
YES : Go to "Control Circuit Inspection" procedure.
NO :
- Check fuse between battery and main relay is disconnected.
- Repair or replace open or short in harness and then go to "Verification of Vehicle Repair" procedure.
CONTROL CIRCUIT INSPECTION
1. Check short in coil control
1. IG "OFF".
2. Disconnect Main Relay and PCM connector.
3. Measure resistance between harness terminal 4 and chassis ground.
4. Measure resistance between harness terminal 4 and 5 of Main Relay.
Specification : Infinite
5. Is the measured resistance within specification?
YES : Go to "Check open in coil control" as follows.
NO : Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
2. Check open in coil control
1. IG "OFF".
2. Disconnect Main Relay and PCM connector.
3. Measure resistance between harness terminal 4 of Main Relay and harness terminal 43 of PCM harness connector.
Specification : Approx. below 1 Ohm
4. Is the measured resistance within specifications?
YES : Go to "Component Inspection" procedure.
NO : Repair or replace as necessary and then, go to "Verification of Vehicle Repair" procedure.
COMPONENT INSPECTION
1. Check Main Relay
1. IG "OFF"
2. Disconnect Main Relay
3. Measure resistance between terminal 5 and 3 of Main Relay
4. Measure resistance between terminal 4 and 2 of Main 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.
NOTE: There is a memory reset function on scantool that can erase optional parts automatically detected and memorized by PCM.
NO : Substitute with a known - good Main Relay and check for proper operation. If the problem is corrected, replace Main 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. Press F4(DTAL) 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 parameter displayed "History (Not Present) fault"?
YES : System performing to specification at this time. Clear the DTC
NO : Go to the applicable troubleshooting procedure.