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

DTC detecting condition: 

Detected when two consecutive driving cycles with fault occur.

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM (IMPREZA MODEL)>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM . Ref. to WIRING SYSTEM (CROSSTREK MODEL (EXCEPT FOR HEV))>ENGINE ELECTRICAL SYSTEM>WIRING DIAGRAM .

• IMPREZA MODEL

  Courtesy of SUBARU OF AMERICA, INC.

• CROSSTREK MODEL

  Courtesy of SUBARU OF AMERICA, INC.

  CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .
  NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Ref. to ENGINE (DIAGNOSTICS) (H4DO 2.0 (EXCEPT FOR HEV))>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

Check the connecting condition of ECM connector.

Is the ECM connector correctly connected?

Yes:  Go to  2.

No:  Connect the ECM connector correctly.

1. Turn the ignition switch to OFF.
2. Remove the main relay.
3. Disconnect the connector from ECM.
4. Measure the resistance between the ECM connector and engine ground.

   Connector and terminal 

   (B134) No. 12 - Engine 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.

1. Turn the ignition switch to ON.
2. Measure the voltage between ECM connector and engine ground.

   Connector and terminal 

   (B134) No. 67 (+) - Engine ground (-):

   (B134) No. 68 (+) - Engine ground (-):

Is the voltage 10 V or more?

Yes:  Repair the harness and connector.

No:  Repair the poor contact of ECM connector.