Fuel Pump Circuit

Wiring diagram:

Engine Electrical System Refer to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

CAUTION: Use the check board when measuring the ECM terminal voltage and resistance. Refer to ENGINE (DIAGNOSTICS) (H4DO)>GENERAL DESCRIPTION>PREPARATION TOOL>HOW TO USE CHECK BOARD .

CHECK OPERATING SOUND OF FUEL PUMP .
Check if the fuel pump operates for two seconds when turning the ignition switch to ON.

NOTE: Fuel pump operation can be executed using the Subaru Select Monitor. Refer to "Active Test" for the procedures. Refer to ENGINE (DIAGNOSTICS) (H4DO)>ACTIVE TEST .

Does the fuel pump emit operating sound?

Yes : Check the fuel injector circuit. Refer to ENGINE (DIAGNOSTICS) (H4DO)>DIAGNOSTICS WITH PHENOMENON>FUEL INJECTOR CIRCUIT .

No : Go to 2.
CHECK GROUND CIRCUIT OF FUEL PUMP (OPEN CIRCUIT) .
1. Turn the ignition switch to OFF.
2. Disconnect the connector from fuel pump.
3. Measure the resistance of harness between fuel pump connector and chassis ground.
  Connector & terminal
  
  (R132) No. 6 - Chassis ground:
Is the resistance less than 5 Ω?

Yes : Go to 3.

No : Repair the following item.
- Open circuit in harness between fuel pump connector and chassis ground
- Poor contact of J/C
CHECK POWER SUPPLY TO FUEL PUMP .
1. Turn the ignition switch to ON.
2. Measure the voltage between fuel pump connector and chassis ground.
  Connector & terminal
  
  (R132) No. 5 (+) - Chassis ground (-):
Is the voltage 10 V or more?

Yes : Replace the fuel pump. Refer to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>FUEL PUMP ASSEMBLY .

No : Go to 4.
CHECK HARNESS BETWEEN FUEL PUMP AND FUEL PUMP RELAY (OPEN) .
1. Turn the ignition switch to OFF.
2. Remove the fuel pump relay.
3. Measure the resistance of harness between fuel pump connector and fuel pump relay connector.
  Connector & terminal
  
  (R132) No. 5 - M/B (fuel pump relay) No. 3:
Is the resistance less than 1 Ω?

Yes : Go to 5.

No : Repair the following item.
- Open circuit in harness between fuel pump connector and fuel pump relay connector
- Poor contact of coupling connector
CHECK HARNESS BETWEEN FUEL PUMP AND FUEL PUMP RELAY (SHORT TO GROUND) .
Measure the resistance between fuel pump connector and chassis ground.

Connector & terminal

(R132) No. 5 - Chassis ground:

Is the resistance 1 MΩ or more?

Yes : Go to 6.

No : Repair the short circuit to ground in harness between fuel pump connector and fuel pump relay connector.
CHECK FUEL PUMP RELAY .
Check the fuel pump relay. Refer to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>FUEL PUMP RELAY .

Is the check result OK?

Yes : Go to 7.

No : Replace the fuel pump relay. Refer to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>FUEL PUMP RELAY .
CHECK HARNESS BETWEEN ECM AND FUEL PUMP RELAY (OPEN) .
1. Disconnect the connector from ECM.
2. Measure the resistance of harness between ECM connector and fuel pump relay connector.
  Connector & terminal
  
  (B62) No. 31 - M/B (fuel pump relay) No. 4:
Is the resistance less than 1 Ω?

Yes : Go to 8.

No : Repair the open circuit of harness between ECM connector and fuel pump relay connector.
CHECK POWER SUPPLY OF FUEL PUMP RELAY .
1. Turn the ignition switch to ON.
2. Measure the voltage between fuel pump relay connector and chassis ground.
  Connector & terminal
  
  M/B (fuel pump relay) No. 1 (+) - Chassis ground (-):
  
  M/B (fuel pump relay) No. 2 (+) - Chassis ground (-):
Is the voltage 10 V or more?

Yes : Repair the poor contact of ECM connector.

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

NOTE: After the faulty parts are repaired or replaced, perform the final check in Basic Diagnostic Procedure. Refer to ENGINE (Diagnostics) (H4DO)>Basic Diagnostic Procedure>PROCEDURE .