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: Power Supply And Ground Line Of Engine Control Module Wiring Diagram

Courtesy of SUBARU OF AMERICA, INC.

DIAGNOSTIC PROCEDURE - CHECK POWER SUPPLY AND GROUND LINE OF ENGINE CONTROL MODULE (ECM)

Step	Check	Yes	No
1 CHECK MAIN RELAY. Turn the ignition switch to OFF. Remove the main relay. Connect the battery to main relay terminals No. 1 and No. 2. 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 OF ECM. Disconnect the connector from ECM. Measure the resistance of harness between ECM and chassis ground. Connector & terminal (B134) No. 7 - Chassis ground: (B134) No. 15 - Chassis ground: (B134) No. 22 - Chassis ground: (B136) No. 1 - Chassis ground: (B137) No. 8 - Chassis ground: (B137) No. 17 - Chassis ground: (B137) No. 18 - Chassis ground: (B84) No. 8 - Chassis ground: (B84) No. 9 - 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 (B84) No. 10 (+) - Chassis ground (-): (B134) No. 5 (+) - 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 HARNESS BETWEEN ECM AND MAIN RELAY CONNECTOR. Turn the ignition switch to OFF. Measure the resistance between ECM and chassis ground. Connector & terminal (B134) No. 6 - Chassis ground:	Is the resistance more than 1 MΩ?	Go to step 5.	Repair the ground short circuit in harness between ECM connector and main relay connector, and then replace ECM.
5 CHECK OUTPUT VOLTAGE FROM ECM. Connect the connector to ECM. Turn the ignition switch to ON. Measure the voltage between ECM connector and chassis ground. Connector & terminal (B134) No. 6 (+) - Chassis ground (-):	Is the voltage more than 10 V?	Go to step 6.	Replace the ECM. < Ref. to ENGINE CONTROL MODULE (ECM) . >
6 CHECK INPUT VOLTAGE OF MAIN RELAY. Check the voltage between main relay connector and chassis ground. Connector & terminal (B47) No. 2 (+) - Chassis ground (-):	Is the voltage more than 10 V?	Go to step 7.	Repair the open circuit in harness between ECM connector and main relay connector.
7 CHECK GROUND CIRCUIT OF MAIN RELAY. Turn the ignition switch to OFF. Measure the resistance between main relay connector and chassis ground. Connector & terminal (B47) No. 1 - Chassis ground:	Is the resistance less than 5 Ω?	Go to step 8.	Repair the open circuit between main relay and chassis ground.
8 CHECK INPUT VOLTAGE OF MAIN RELAY. Measure the voltage between main relay connector and chassis ground. Connector & terminal (B47) No. 5 (+) - Chassis ground (-): (B47) No. 6 (+) - Chassis ground (-):	Is the voltage more than 10 V?	Go to step 9.	Repair the open or ground short circuit in harness of power supply circuit.
9 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 (B84) No. 2 (+) - Chassis ground (-): (B84) No. 3 (+) - Chassis ground (-):	Is the voltage 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.