Fuel Pump Circuit

Wiring diagram: 

Engine Electrical System Ref. to WIRING SYSTEM>Engine Electrical System>WIRING DIAGRAM .

Courtesy of SUBARU OF AMERICA, INC.

1. 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. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>ACTIVE TEST .

   Does the fuel pump emit operating sound?

   Yes  : Check the fuel injector circuit. Ref. to ENGINE (DIAGNOSTICS) (H4DOTC)>Diagnostics with Phenomenon>FUEL INJECTOR CIRCUIT .

   No  : Go to  2.

2. CHECK GROUND CIRCUIT OF FUEL PUMP CONTROL UNIT (OPEN)  .
   1. Turn the ignition switch to OFF.
   2. Disconnect the connector from fuel pump control unit.
   3. i Measure the resistance of harness between fuel pump control unit connector and chassis ground.

      Connector & terminal 

      (R122) No. 4 - Chassis ground:

   Is the resistance less than 5 Ω?

   Yes  : Go to  3.

   No  : Repair the open circuit in harness between fuel pump control unit connector and chassis ground.

3. CHECK FUEL PUMP CONTROL UNIT POWER SUPPLY  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between fuel pump control unit connector and chassis ground.

      Connector & terminal 

      (R122) No. 1 (+) - Chassis ground (-):

   Is the voltage 10 V or more?

   Yes  : Go to  4.

   No  : Go to  5.

4. CHECK OF FUEL PUMP  .
   1. Turn the ignition switch to OFF.
   2. Check fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel Pump>INSPECTION .

   Is the check result OK?

   Yes  : Repair the poor contact of fuel pump control unit connector.

   No  : Replace the fuel pump. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel Pump>REMOVAL .

5. CHECK HARNESS BETWEEN FUEL PUMP CONTROL UNIT AND M/B (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 control unit connector and M/B (fuel pump relay).

      Connector & terminal 

      (R122) No. 1 - M/B (fuel pump relay) No. 3:

   Is the resistance less than 1 Ω?

   Yes  : Go to  6.

   No  : Repair the following item.

   • Open circuit in harness between fuel pump control unit connector and M/B (fuel pump relay)
   • Poor contact of coupling connector
6. CHECK HARNESS BETWEEN FUEL PUMP CONTROL UNIT AND M/B (FUEL PUMP RELAY) (SHORT TO GROUND)  .

   Measure the resistance of harness between fuel pump connector and M/B (fuel pump relay).

   Connector & terminal 

   (R122) No. 1 - Chassis ground:

   Is the resistance 1 MΩ or more?

   Yes  : Go to  7.

   No  : Repair the short circuit to ground in harness between fuel pump control unit connector and M/B (fuel pump relay).

7. CHECK FUEL PUMP RELAY. \ 

   Check the fuel pump relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>Fuel Pump Relay>INSPECTION .

   Is the check result OK?

   Yes  : Go to  8.

   No  : Replace the fuel pump relay. Ref. to FUEL INJECTION (FUEL SYSTEMS) (H4DOTC)>FUEL PUMP RELAY .

8. CHECK POWER SUPPLY OF M/B (FUEL PUMP RELAY)  .
   1. Turn the ignition switch to ON.
   2. Measure the voltage between M/B (fuel pump relay) 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  : Go to  9.

   No  : Repair the following item.

   • Blown out of fuse
   • Defective F/B (IG2 relay)
   • Poor contact of F/B (IG2 relay)
9. CHECK GROUND CIRCUIT OF M/B (FUEL PUMP RELAY) (OPEN)  .
   1. Turn the ignition switch to OFF.
   2. Measure the resistance in harness between M/B (fuel pump relay) terminal and engine ground.

      Connector & terminal 

      No. 4 - Engine ground:

   Is the resistance less than 5 Ω?

   Yes  : Repair the poor contact of fuel pump control unit connector.

   No  : Repair the open circuit between M/B (fuel pump relay) and engine ground.