Fuel Pump Circuit

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

Wiring diagram: Engine Electrical System Ref. to WIRING SYSTEM>ENGINE ELECTRICAL SYSTEM .

Courtesy of SUBARU OF AMERICA, INC.

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.
- For detailed operation procedures, refer to the "Active Test". Ref. to ENGINE (DIAGNOSTICS) (H4DO)>ACTIVE TEST .
Does the fuel pump emit operating sound?

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

No: Go to 2.
CHECK GROUND CIRCUIT OF FUEL PUMP .
1. Turn the ignition switch to OFF.
2. Remove the service hole cover of fuel pump.
3. Disconnect the connector from fuel pump.
4. 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 open circuit in harness between fuel pump connector and chassis ground.
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. Ref. 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 the harness between fuel pump connector and M/B (fuel pump relay) terminal No. 3.
  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 M/B (fuel pump relay)
  - Poor contact of coupling connector
CHECK HARNESS BETWEEN FUEL PUMP AND FUEL PUMP RELAY (SHORT TO GROUND) .
Measure the resistance between the fuel pump connector and fuel pump relay.

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 the harness between fuel pump connector and M/B (fuel pump relay).
CHECK FUEL PUMP RELAY .
1. Remove the fuel pump relay.
2. Check the fuel pump relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DO)>FUEL PUMP RELAY>INSPECTION .
  Is the check result OK?
  
  Yes: Go to 7.
  
  No: Replace the fuel pump relay. Ref. 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 the harness between ECM connector and M/B (fuel pump relay) terminal No. 4.
  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 the harness between ECM connector and M/B (fuel pump relay).
CHECK POWER SUPPLY OF FUEL PUMP RELAY .
1. Turn the ignition switch to ON.
2. Measure the voltage between M/B (fuel pump relay) terminal No. 1 and No. 2 and engine ground.
  Connector & terminal
  
  M/B (fuel pump relay) No. 1 (+) - Engine ground (-):
  
  M/B (fuel pump relay) No. 2 (+) - Engine 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. Ref. to ENGINE (DIAGNOSTICS) (H4DO)>BASIC DIAGNOSTIC PROCEDURE>PROCEDURE .