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HOMESERVICE MANUALSSUBARU2016LEGACY 2.5IREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT VARIANT/TRIMSECTION 15 (ENGINE CONTROLS (H6DO) (DIAGNOSTICS) (4 OF 5))DIAGNOSTIC PROCEDURE WITH DIAGNOSTIC TROUBLE CODE (DTC)DTC P0685 ECM/PCM POWER RELAY CONTROL CIRCUIT/OPENWIRING DIAGRAM
2016 Subaru Legacy 2.5i

DTC P0685 ECM/Pcm Power Relay Control Circuit/Open: Wiring Diagram

2016 Subaru Legacy 2.5iSECTION Wiring Diagram
WARNING: This page is about a different variant/trim than selected.
  • Engine Electrical System ENGINE TYPE EZ (WITHOUT PUSH BUTTON START) < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. >
  • Engine Electrical System ENGINE TYPE EZ (WITH PUSH BUTTON START) < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. >
    Fig 1: Main Relay - Circuit Diagram
    G10264426Courtesy of SUBARU OF AMERICA, INC.
DIAGNOSTIC PROCEDURE

Step Check Yes No
1 CHECK ECM CONNECTOR. 
Check the connecting condition of ECM connector.		 Is the ECM connector correctly connected? Go to step 2  . Connect the ECM connector correctly.
2 CHECK HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Measure the voltage between ECM connector and engine ground.

    Connector & terminal 

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

    (B134) No. 14 (+) - Engine ground (-): 

 Is the voltage 10 V or more? 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
 Go to step 3  .
3 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? Repair the poor contact of ECM connector. Repair the short circuit to ground in harness between ECM connector and main relay connector.
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.