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

CAUTION:

After servicing or replacing faulty parts, perform Clear Memory Mode. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>CLEAR MEMORY MODE>OPERATION ., and inspection mode. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>INSPECTION MODE>PROCEDURE .
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 .

Courtesy of SUBARU OF AMERICA, INC.

CHECK MAIN RELAY .
1. Turn the ignition switch to OFF.
2. Remove the main relay.
3. Check the main relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>MAIN RELAY>INSPECTION .
  Is the check result OK?
  
  Yes
  
  Go to 2 .
  
  No
  
  Replace the main relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>MAIN RELAY .
CHECK GROUND CIRCUIT FOR ECM .
1. Disconnect the connector from ECM.
2. Measure the resistance of harness between ECM connector and chassis ground.
  Connector & terminal
  
  (E158) No. 61 - Chassis ground:
  
  (E158) No. 62 - Chassis ground:
  
  (E158) No. 63 - Chassis ground:
  
  (E158) No. 64 - Chassis ground:
  
  (E158) No. 65 - Chassis ground:
  
  Is the resistance less than 5 Ω?
  
  Yes
  
  Go to 3 .
  
  No
  
  Open circuit of harness between ECM connector and engine ground terminal
CHECK INPUT VOLTAGE OF ECM .
1. Turn the ignition switch to ON.
2. Measure the voltage between ECM connector and chassis ground.
  Connector & terminal
  
  (B134) No. 2 (+) - Chassis ground (-):
  
  (B134) No. 27 (+) - Chassis ground (-):
  
  Is the voltage 10 V or more?
  
  Yes
  
  Go to 4 .
  
  No
  
  Repair the open or ground short in the harness of power supply circuit.
CHECK INPUT VOLTAGE OF MAIN RELAY .
Measure the voltage between M/B (main relay) terminal and chassis ground. Terminals

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

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

Is the voltage 10 V or more?

Yes

Go to 5 .

No

Repair the open or ground short in the harness of power supply circuit.
CHECK INPUT VOLTAGE OF ECM .
1. Turn the ignition switch to OFF.
2. Install the main relay.
3. Measure the voltage between ECM connector and chassis ground.
  Connector & terminal
  
  (B134) No. 60 (+) - Chassis ground (-):
  
  Is the voltage 10 V or more?
  
  Yes
  
  Go to 6 .
  
  No
  
  Repair the open circuit of harness between ECM connector and M/B (main relay) terminal.
CHECK INPUT VOLTAGE OF ECM .
1. Connect the connector to ECM.
2. Turn the ignition switch to ON.
3. Measure the voltage between ECM connector and chassis ground.
  Connector & terminal
  
  (B134) No. 1 (+) - Chassis ground (-):
  
  (B134) No. 14 (+) - Chassis ground (-):
  
  Is the voltage 10 V or more?
  
  Yes
  
  Check ignition control system. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>DIAGNOSTICS FOR ENGINE STARTING FAILURE>IGNITION CONTROL SYSTEM .
  
  No
  
  Repair the harness and connector.
  NOTE:
  In this case, repair the following item:
  - Open circuit of harness between ECM connector and M/B (main relay) connector
  - Poor contact of M/B (main relay) connector
  - Poor contact of ECM connector