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

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM (CROSSTREK MODEL (HEV))>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

1. CHECK FOR MALFUNCTION STATUS  .

   Check for the generating condition of starting failure.

   Has the start failure occurred during Auto Start Stop or during EV traveling?

   Yes:  Check the hybrid system. Ref. to P-HEV HYBRID POWERTRAIN CONTROL (DIAGNOSTICS)>BASIC DIAGNOSTIC PROCEDURE .

   No:  Go to  2.

2. CHECK M/B (MAIN RELAY)  .
   1. Turn the ignition switch to OFF.
   2. Remove the M/B (main relay).
   3. Check the M/B (main relay). Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO(HEV))>MAIN RELAY>INSPECTION .

   Is the check result OK?

   Yes:  Go to  3.

   No:  Replace the M/B (main relay). Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO(HEV))>MAIN RELAY .

3. CHECK GROUND CIRCUIT FOR ECM  .
   1. Disconnect the connector from ECM.
   2. Measure the resistance of harness between ECM connector and engine ground.

   Connector and terminal 

   (B134) No. 69 - Engine ground:

   (B134) No. 70 - Engine ground:

   (B134) No. 71 - Engine ground:

   (B134) No. 72 - Engine ground:

   Is the resistance less than 5 Ω?

   Yes:  Go to  4.

   No:  Repair the harness and connector.

   NOTE:

   In this case, repair the following item: 

   • Open circuit of harness between ECM connector and engine ground 
   • Poor contact of coupling connector 
4. CHECK INPUT VOLTAGE OF ECM  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between ECM connector and engine ground.

   Connector and terminal 

   (B134) No. 1 (+) - Engine ground (-):

   (B134) No. 56 (+) - Engine 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.

5. CHECK M/B (MAIN RELAY) INPUT VOLTAGE  .

   Measure the voltage between M/B (main relay) terminal and engine ground.

   Terminal 

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

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

   Is the voltage 10 V or more?

   Yes:  Go to  6.

   No:  Repair the open or ground short in the harness of power supply circuit.

6. CHECK INPUT VOLTAGE OF ECM  .
   1. Turn the ignition switch to OFF.
   2. Install the M/B (main relay).
   3. Measure the voltage between ECM connector and engine ground.

   Connector and terminal 

   (B134) No. 12 (+) - Engine ground (-):

   Is the voltage 10 V or more?

   Yes:  Go to  7.

   No:  Repair the open circuit of harness between ECM connector and M/B (main relay) terminal.

7. 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 engine ground.

   Connector and terminal 

   (B134) No. 67 (+) - Engine ground (-):

   (B134) No. 68 (+) - Engine ground (-):

   Is the voltage 10 V or more?

   Yes:  Check ignition control system. Ref. to ENGINE (DIAGNOSTICS) (H4DO(HEV))>DIAGNOSTICS WITH PHENOMENON>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