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DTC P0685: ECM/Pcm Power Relay Control Circuit/Open: Notes

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

CAUTION: After servicing or replacing faulty parts, perform Clear Memory Mode Ref. to ENGINE (DIAGNOSTICS) (STI)>Clear Memory Mode>OPERATION , and Inspection Mode Ref. to ENGINE (DIAGNOSTICS) (STI)>Inspection Mode>PROCEDURE .

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

G12456948

Courtesy of SUBARU OF AMERICA, INC.

CHECK ECM CONNECTOR .
Check the connecting condition of ECM connector.

Is the ECM connector correctly connected?

Yes: Go to 2

No: Connect the ECM connector correctly.
CHECK HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR .
1. Turn the ignition switch to OFF.
2. Remove the main relay.
3. Disconnect the connector from ECM.
4. Measure the resistance between ECM connector and chassis ground.
  Connector & terminal
  
  (B135) No. 13 - Chassis ground:
Is the resistance 1 MΩ or more?

Yes: Go to 3

No: Repair the short circuit to ground in harness between ECM connector and main relay connector.
CHECK HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR .
1. Install the main relay.
2. Turn the ignition switch to ON.
3. Measure the voltage between ECM connector and chassis ground.
  Connector & terminal
  
  (B136) No. 1 (+) - Chassis ground (-):
  
  (B137) No. 7 (+) - Chassis ground (-):
Is the voltage 10 V or more?

Yes: Repair the harness and connector.
NOTE:
In this case, repair the following item:
- Short circuit to power supply in harness between ECM connector and main relay connector
- Defective main relay
No: Repair the poor contact of ECM connector.