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HOMESERVICE MANUALSSUBARU2016LEGACY 2.5IREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROLS (H4DO) (DIAGNOSTICS - INTRODUCTION)DIAGNOSTICS FOR ENGINE STARTING FAILUREFUEL PUMP CIRCUITWIRING DIAGRAM
2016 Subaru Legacy 2.5i

Fuel Pump Circuit: Wiring Diagram

2016 Subaru Legacy 2.5iSECTION Wiring Diagram
  • Engine Electrical System ENGINE TYPE FB (WITHOUT PUSH BUTTON START) < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. >
  • Engine Electrical System ENGINE TYPE FB (WITH PUSH BUTTON START) < Ref. to appropriate wiring diagram in SYSTEM WIRING DIAGRAM article. >
    Fig 1: Fuel Pump Circuit Diagram
    G10263261Courtesy of SUBARU OF AMERICA, INC.
DIAGNOSTIC PROCEDURE

Step Check Yes No
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 ACTIVE TEST . >		 Does the fuel pump emit operating sound? Check the fuel injector circuit. < Ref. to FUEL INJECTOR CIRCUIT , Diagnostics for Engine Starting Failure. > Go to step 2  .
2 CHECK GROUND CIRCUIT OF FUEL PUMP. 
  1. Turn the ignition switch to OFF.
  2. Remove the fuel pump access hole lid.
  3. Disconnect the connector from fuel pump.
  4. Measure the resistance of harness between fuel pump and chassis ground.

    Connector & terminal 

    (R58) No. 6 - Chassis ground: 

 Is the resistance less than 5 Ω? Go to step 3  . Repair the open circuit in harness between fuel pump connector and chassis ground terminal.
3 CHECK POWER SUPPLY TO FUEL PUMP. 
  1. Turn the ignition switch to ON.
  2. Measure the voltage of power supply circuit between fuel pump connector and chassis ground.

    Connector & terminal 

    (R58) No. 5 (+) - Chassis ground (-): 

 Is the voltage 10 V or more? Replace the fuel pump. < Ref. to FUEL PUMP . > Go to step 4  .
4 CHECK HARNESS BETWEEN FUEL PUMP AND FUEL PUMP RELAY CONNECTOR. 
  1. Turn the ignition switch to OFF.
  2. Measure the resistance of harness between fuel pump connector and fuel pump relay connector.

    Connector & terminal 

    (R58) No. 5 - (B48) No. 45: 

 Is the resistance less than 1 Ω? Go to step 5  . Repair the harness and connector.
NOTE: In this case, repair the following item:
  • Open circuit in harness between fuel pump connector and fuel pump relay connector
  • Poor contact of coupling connector
5 CHECK HARNESS BETWEEN FUEL PUMP AND FUEL PUMP RELAY CONNECTOR. 
Measure the resistance of harness between fuel pump connector and fuel pump relay connector.
Connector & terminal 
(R58) No. 5 - Chassis ground: 		 Is the resistance 1 MΩ or more? Go to step 6  . Repair the short circuit to ground in harness between fuel pump connector and fuel pump relay connector.
6 CHECK FUEL PUMP RELAY. 
  1. Remove the fuel pump relay.
  2. Connect the battery to fuel pump relay terminals No. 43 and No. 42.
  3. Measure the resistance between fuel pump relay terminals.

    Terminals 

    No. 44 - No. 45: 

 Is the resistance less than 1 Ω? Go to step 7  . Replace the fuel pump relay. < Ref. to FUEL PUMP RELAY . >
7 CHECK HARNESS BETWEEN ECM AND FUEL PUMP RELAY CONNECTOR. 
  1. Disconnect the connector from ECM.
  2. Measure the resistance of harness between ECM connector and fuel pump relay connector.

    Connector & terminal 

    (B134) No. 63 - (B48) No. 42: 

 Is the resistance less than 1 Ω? Go to step 8  . Repair the open circuit of harness between ECM connector and fuel pump relay connector.
8 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 

    (B48) No. 43 (+) - Chassis ground (-): 

    (B48) No. 22 (+) - Chassis ground (-): 

 Is the voltage 10 V or more? Repair the poor contact of ECM connector. Repair the open or ground short in the harness of power supply circuit.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.