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

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>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)>Basic Diagnostic Procedure>PROCEDURE .

Wiring diagram:

Engine Electrical System Ref. to WIRING SYSTEM (CROSSTREK MODEL)>Engine Electrical System>WIRING DIAGRAM .

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 (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.