P0685

COMPONENT LOCATION





GENERAL DESCRIPTION

The ECM provides ground to one side of the coil of the main relay and the other side is connected to the battery. The ECM 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., ECM sets P0685.

DTC DETECTING CONDITION





** If Main relay has a fault(ex. Open) while the engine is running, the DTCs,P0638/P0685/P1295/P2106, can happen at the same time.

- P0638 Throttle Actuator Control Range/Performance(Bank 1)
- P0685 ECM/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 "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 ECM's connector or was repaired and ECM 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. IG "OFF"
2. Disconnect Main Relay
3. IG "ON" & ENG "OFF".
4. Measure the voltage between terminal 30 of main relay harness connector and chassis ground.
5. Measure the voltage between terminal 86 of main relay harness connector 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 harness
(1) IG "OFF".
(2) Disconnect Main Relay and ECM connector.
(3) Measure resistance between terminal 86 of Main Relay and chassis ground.
(4) Measure resistance between terminals 86 and 85 of Main Relay.

Specification : Infinite

(5) 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.
2. Check open in harness
(1) IG "OFF".
(2) Disconnect Main Relay and ECM connector.
(3) Measure resistance between harness terminal 85 of Main Relay and harness terminal 43 of ECM harness connector(C144-A).

Specification : Approx. below 1Ohms

(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 the resistance between terminal 30 and 87 of main relay.
(4) Measure the resistance between terminal 85 and 86 of main relay.
Specification :

(5) Is the measured resistance within specification ?
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 ECM.

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 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.