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HOMESERVICE MANUALSSUBARU2005OUTBACK I, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS - ENGINE (DIAGNOSTICS) (H4SO)DIAGNOSTICS FOR ENGINE STARTING FAILURECHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM)
2005 Subaru Outback i, Standard

Check Power Supply And Ground Line Of Engine Control Module (ECM)

2005 Subaru Outback i, StandardSECTION Check Power Supply And Ground Line Of Engine Control Module (ECM)
CAUTION: After repair or replacement of faulty parts, conduct Clear Memory Mode < Ref. to , CLEAR MEMORY MODE . > and Inspection Mode < Ref. to , INSPECTION MODE . >.

WIRING DIAGRAM: 

Fig 1: Wiring Diagram - Engine Control Module Power Supply And Ground Line
G03828438Courtesy of SUBARU OF AMERICA, INC.
ECM DIAGNOSIS

Step Check Yes No
1. CHECK MAIN RELAY. 
  1. Turn the ignition switch to OFF.
  2. Remove the main relay.
  3. Connect the battery to main relay terminals No. 1 and No. 2.
  4. Measure the resistance between main relay terminals.

    Terminals 

    No. 3 - No. 5: 

    No. 4 - No. 6: 

 Is the resistance less than 10 Ω? Go to step 2.  Replace the main relay.
2. CHECK GROUND CIRCUIT FOR ECM. 
  1. Disconnect the connector from ECM.
  2. Measure the resistance of harness between ECM and chassis ground.

    Connector & terminal 

    (B134) No. 6 - Chassis ground: 

    (B134) No. 7- Chassis ground: 

    (B135) No. 1 - Chassis ground: 

    (B135) No. 4 - Chassis ground: 

    (B135) No. 12 - Chassis ground: 

    (B137) No. 1 - Chassis ground: 

    (B137) No. 2 - Chassis ground: 

    (B137) No. 3 - Chassis ground: 

    (B137) No. 7 - Chassis ground: 

 Is the resistance less than 5 Ω? Go to step 3.  Repair the open circuit in harness between ECM connector and engine grounding terminal.
3. CHECK INPUT VOLTAGE OF ECM. 
Measure the voltage between ECM connector and chassis ground.
Connector & terminal 
(B135) No. 19 (+) - Chassis ground (-): 
(B137) No. 15 (+) - Chassis ground (-): 		 Is the voltage more than 10 V? Go to step 4.  Repair the open or ground short circuit of power supply circuit.
4. CHECK INPUT VOLTAGE OF MAIN RELAY. 
Measure the voltage between main relay connector and chassis ground.
Connector & terminal 
(B47) No. 1 (+) - Chassis ground (-): 
(B47) No. 5 (+) - Chassis ground (-): 
(B47) No. 6 (+) - Chassis ground (-): 		 Is the voltage more than 10 V? Go to step 5.  Repair the open or ground short circuit in harness of power supply circuit.
5. CHECK INPUT VOLTAGE OF ECM. 
  1. Turn the ignition switch to ON.
  2. Measure the voltage between ECM connector and chassis ground.

    Connector & terminal 

    (B135) No. 5 (+) - Chassis ground (-): 

    (B135) No. 6 (+) - Chassis ground (-): 

    (B137) No. 17 (+) - Chassis ground (-): 

 Is the voltage more than 10 V? Check ignition control system. < Ref. to , IGNITION CONTROL SYSTEM , Diagnostics for Engine Starting Failures Repair the open or ground short circuit in harness between ECM connector and main relay connector.
RENDER: 1.0x

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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.