P0685

DTC P0685






GENERAL DESCRIPTION
One terminal of main relay is connected to battery and the other terminal which is ground point is connected to PCM. PCM monitors the voltages flowing into main relay and going through it.

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

SPECIFICATION
Coil Resistance: 70 ohms - 120 ohms

Schematic Diagram:

SCHEMATIC DIAGRAM

MONITOR SCANTOOL DATA
1. Connect Scantool to DLC (Data Link Connector)
2. Warm up the engine to normal operating temperature.




3. Monitor "Main Relay" parameter on Scantool.
4. Is the "Main Relay" parameter displayed correctly?

YES - Fault is intermittent caused by poor contact in 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

NO - Go to "Terminal and Connector Inspection" 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
a. IG "OFF".
b. Disconnect Main Relay and PCM connector.
c. Measure resistance between harness terminal 4 and chassis ground.




d. Measure resistance between harness terminal 4 and 5 of Main Relay.

Specification : Infinite

e. 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
a. IG "OFF".
b. Disconnect Main Relay and PCM connector.




c. Measure resistance between harness terminal 4 of Main Relay and harness terminal 43 of PCM harness connector.

Specification : Approx. below 1 ohm

d. 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
a. IG "OFF"
b. Disconnect Main Relay
c. Measure resistance between terminal 5 and 3 of Main Relay

Specification:

d. Measure resistance between terminal 4 and 2 of Main Relay.
e. 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. Monitor and record the Freeze Frame Data for the Diagnostic Trouble Code(DTC) which has been diagnosed.
2. Using a Scantool, Clear the DTCs
3. Operate the vehicle within conditions noted in the freeze frame data or enable conditions
4. Monitor that all readiness test have been verified as "Complete".
5. Are any DTCs present?

YES - Go to the applicable troubleshooting procedure.

NO - System is performing to specification at this time.