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

1. -

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Wiring diagram:

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

G12400087

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Refer to ENGINE (DIAGNOSTICS) (H4DO (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. Refer to ENGINE (DIAGNOSTICS) (H4DO (EXCEPT FOR HEV))>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .

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 (SHORT TO GROUND) .
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 & 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.
CHECK HARNESS BETWEEN ECM AND MAIN RELAY (SHORT TO POWER SUPPLY) .
1. Turn the ignition switch to ON.
2. Measure the voltage between ECM connector and engine ground.
  Connector & terminal
  
  (B134) No. 67 (+) - Engine ground (-):
  
  (B134) No. 68 (+) - Engine 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.