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:
* If Main relay has a fault(ex. Open) while the engine is running, the DTCs,P0638lP0685/P1295lP2106, can happen at the same time.
< DTC Name >
- P0638 Throttle Actuator Control Range/Performance(Bank 1)
- P0685 PCM/PCM Power Relay Control Circuit /Open
- P1295 Throttle Actuator Control System - Power Management
- P2106 Throttle Actuator Control System - Forced Limited Power
Specification:
Schematic Diagram:
MONITOR DTC STATUS
1. Check DTC Status
1. Connect scantool to Data Link Connector(DLC).
2. IG "ON".
3. Select "DTC" button, and then Press "DTC Status" 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, bending, 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
- CHECK VOLTAGE
1. IG "OFF".
2. Disconnect the main relay.
3. IG "ON" and ENG "OFF"
4. Measure the voltage between power supply terminals of main relay harness connector and chassis ground.
Specification : B+
5. 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
- CHECK SHORT IN HARNESS
1. IG "OFF"
2. Disconnect main relay and PCM connector.
3. Measure the resistance between control terminal of main relay harness connector and chassis ground.
Specification : Infinite
4. Is the measured resistance within specification?
YES - Go to "Check open in harness" as follows.
NO - Repair or replace as necessary and then go to "Verification of Vehicle Repair" procedure.
- CHECK OPEN IN HARNESS
1. IG "OFF".
2. Disconnect main relay and PCM connector.
3. Measure the resistance between control terminal of main relay harness connector and main relay control terminal 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
- CHECK MAIN RELAY
1. IG "OFF".
2. Disconnect the main relay.
3. Measure the resistance between battery power supply and control terminals of main relay.(Measurement "A")
4. Measure the resistance between battery power supply and power supply to PCM terminals of main relay.(Measurement "B")
Specification : 70 - 120 ohms
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. Before or after testing PCM on the vehicle, use this function to reuse the PCM on the others.
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 scantool and select "DTC" button.
2. Press "DTC Status" button and confirm that "DTC Readiness Flag" indicates "Completed". 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.