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Home >> Subaru >> 2010 >> Legacy Premium, Standard >> Repair and Diagnosis >> External Pages >> Different variant/trim >> Section 15 (Engine Controls - Engine (Diagnostics) (H4DOTC - 2.5L DOHC Turbo)) >> Diagnostics for Engine Starting Failure >> Check Power Supply And Ground Line Of Engine Control Module (ECM) >> Wiring Diagram

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

WARNING: This page is about a different variant/trim than selected.
Fig 1: Engine Control Module - Wiring Diagram
G06647751Courtesy of SUBARU OF AMERICA, INC.
DIAGNOSTIC PROCEDURE

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. 4: 

 Is the resistance less than 1 Ω? Go to step 2  . Replace the main relay. Ref. to ELECTRICAL COMPONENT LOCATION .
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. 3 - Chassis ground: 

    (B134) No. 4 - Chassis ground: 

    (B134) No. 6 - Chassis ground: 

    (B137) No. 1 - Chassis ground: 

    (B137) No. 3 - Chassis ground: 

 Is the resistance less than 5 Ω? Go to step 3  . Repair the harness and connector.
NOTE: In this case, repair the following item:
  • Open circuit in harness between ECM and engine ground terminal
  • Poor contact of coupling connector
3 CHECK INPUT VOLTAGE OF ECM  .
  1. Turn the ignition switch to ON.
  2. Measure the voltage between ECM and chassis ground.

    Connector & terminal 

    (B136) No. 2 (+) - Chassis ground (-): 

    (B136) No. 30 (+) - Chassis ground (-): 

 Is the voltage 10 V or more? Go to step 4  . Repair the open or ground short circuit of harness of power supply circuit.
4 CHECK INPUT VOLTAGE OF MAIN RELAY  .
Measure the voltage between main relay connector and chassis ground.
Connector & terminal 
(B220) No. 1 (+) - Chassis ground (-): 
(B220) No. 4 (+) - Chassis ground (-): 		 Is the voltage 10 V or more? Go to step 5  . Repair the open or ground short circuit of harness of power supply circuit.
5 CHECK INPUT VOLTAGE OF ECM  .
  1. Turn the ignition switch to OFF.
  2. Install the main relay.
  3. Turn the ignition switch to ON.
  4. Measure the voltage between ECM and chassis ground.

    Connector & terminal 

    (B135) No. 13 (+) - Chassis ground (-): 

 Is the voltage 10 V or more? Go to step 6  . Repair the open circuit in harness between ECM and main relay connector.
6 CHECK INPUT VOLTAGE OF ECM  .
  1. Turn the ignition switch to OFF.
  2. Connect the connector to ECM.
  3. Turn the ignition switch to ON.
  4. Measure the voltage between ECM and chassis ground.

    Connector & terminal 

    (B136) No. 1 (+) - Chassis ground (-): 

    (B137) No. 7 (+) - Chassis ground (-): 

 Is the voltage 10 V or more? Check ignition control system. Ref. to IGNITION CONTROL SYSTEM , Diagnostics for Engine Starting Failure. Repair the harness and connector.
NOTE: In this case, repair the following item:
  • Open circuit in harness between ECM and main relay connector
  • Poor contact of main relay connector
  • Poor contact of ECM connector
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