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 , OPERATION , Clear Memory Mode. > and Inspection Mode < Ref. to , PROCEDURE , Inspection Mode. >.

WIRING DIAGRAM: 

Fig 1: Wiring Diagram - ECM

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE - ECM

Step	Check	Yes	No
1 CHECK MAIN RELAY.  Turn the ignition switch to OFF. Remove the main relay. Using a lead wire, connect the terminal No. 1 of main relay to positive terminal of battery, and terminal No. 2 to ground terminal of battery. Measure the resistance between main relay terminals. Terminals  No. 3 - No. 5:  No. 4 - No. 6:	Is the measured value less than 10 Ω?	Go to step 2.	Replace the main relay.
2 CHECK GROUND CIRCUIT OF ECM.  Disconnect the connector from ECM. Measure the resistance of harness between ECM and chassis ground. Connector & terminal  (B134) No. 6 - Chassis ground:  (B134) No. 7 - Chassis ground:  (B135) No. 12 - Chassis ground:  (B137) No. 3 - Chassis ground:  (B137) No. 1 - Chassis ground:  (B137) No. 2 - Chassis ground:  (B135) No. 1 - Chassis ground:  (B135) No. 4 - Chassis ground:  (B137) No. 7 - Chassis ground:	Is the measured value less than 5 Ω?	Go to step 3.	Repair the open circuit in harness between ECM connector and engine grounding terminal or poor contact in connector.
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 measured value 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 measured value 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.  Connect the main relay connector. Turn the ignition switch to ON. 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 measured value more than 10 V?	Check the ignition control system. < Ref. to , IGNITION CONTROL SYSTEM , Diagnostics for Engine Starting Failure. >	Repair the open or ground short circuit in harness between ECM connector and main relay connector.