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

WARNING: This page is about a different variant/trim than selected.

DTC detecting condition:

Detected when two consecutive driving cycles with fault occur.

Trouble symptom:

Hard to start
Improper idling
Poor driving performance

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Clear Memory Mode . and Inspection Mode Ref. to ENGINE (DIAGNOSTICS) (H4DO)>Inspection Mode .
Use the check board when measuring the ECM terminal voltage and resistance.

Wiring diagram:

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

Fig 1: ECM/PCM Power Relay Control Circuit/Open - Wiring Diagram

G11272673

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 the ECM connector and engine ground.
Connector & terminal

(B134) No. 60 - 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 CONNECTOR .
1. Install the main relay.
2. Turn the ignition switch to ON.
3. Measure the voltage between ECM connector and engine ground.
Connector & terminal

(B134) No. 1 (+) - Engine ground (-):

(B134) No. 17 (+) - 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.