Fuel Pump Electrical Circuit Diagnosis

Fuel Pump Electrical Circuit Diagnosis

Circuit Description

When the ignition switch is turned ON, the control module energizes the fuel pump relay which applies power to the in-tank fuel pump. The fuel pump relay will remain on as long as the engine is running or cranking and the control module is receiving reference pulses. If no reference pulses are present, the control module de-energizes the fuel pump relay within 2 seconds after the ignition is turned ON or the engine is stopped.

Diagnostic Aids

Listen for an audible hiss from the fuel pump when the fuel pump relay is commanded ON. A vibration in the fuel feed line when the fuel pump relay is commanded ON indicates that the fuel pump is operating.

For an intermittent condition, Refer to Intermittent Conditions. Intermittent Conditions

Test Description

Step 1 - Step 10:

Step 11 - Step 21:

The numbers below refer to the step numbers on the diagnostic table:
2. Command both the ON and OFF states. Repeat the commands as necessary.
3. This step determines if the condition is located on the coil side or the switch side of the circuit.
7. This step tests for a grounded voltage supply circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump voltage supply circuit.
9. This step verifies that the fuel pump fuse is providing voltage to the fuel pump relay.
10. This step jumps the fuel pump relay in order to activate the fuel pump.
15. This step determines if the condition with the circuit is intermittent. If the fuse does not open, inspect the supply voltage circuit between the fuse and the fuel pump for an intermittent condition.