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

Fig 1: Identifying Power Supply And Ground Line Of Engine Control Module (ECM) - Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE CHART

Step	Check	Yes	No
1 CHECK MAIN RELAY. Turn the ignition switch to OFF. Remove the main relay. Using the lead wire, connect the battery (+) to the terminal No. 1 of main relay, and the battery (-) to the terminal No. 2. Measure the resistance between main relay terminals. Terminals No. 3 - No. 6: No. 4 - No. 5:	Is the resistance less than 10 Ω?	Go to step 2.	Replace the main relay.
2 CHECK GROUND CIRCUIT FOR ECM. Disconnect the connectors from the ECM. Measure the resistance of harness between ECM and chassis ground. Connector & terminal (B134) No. 5 - 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 of harness or poor contact in the connector between ECM connector and engine grounding terminal.
3 CHECK INPUT VOLTAGE OF ECM. Turn the ignition switch to ON. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B135) No. 5 (+) - Chassis ground (-): (B135) No. 27 (+) - Chassis ground (-):	Is the voltage 10 V or more?	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 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. Connect the main relay connector. Turn the ignition switch to ON. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B135) No. 2 (+) - Chassis ground (-): (B134) No. 7 (+) - Chassis ground (-): (B136) No. 24 (+) - Chassis ground (-):	Is the voltage 10 V or more?	Check the ignition control system. <Ref. to IGNITION CONTROL SYSTEM , Diagnostics For Engine Starting Failure .>	Repair the open or ground short circuit of harness between ECM connector and main relay connector.