Fuel Pump Electrical Circuit Diagnosis

FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS

CIRCUIT DESCRIPTION
When you turn ON the ignition switch, the control module enables the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops.

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.

If the condition is intermittent, refer to Intermittent Conditions. Diagnostic Strategies

TEST DESCRIPTION

Steps 1-4:

Steps 5-11:

Steps 12-14:

Steps 15-18:

Steps 19-24:

Steps 25-29:

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.
4. This step verifies that the PCM is providing voltage to the fuel pump relay.
5. This step tests for an open in the fuel pump relay ground circuit.
6. This step determines if a voltage is constantly being applied to the fuel pump relay.
12. This tests for a grounded fuel pump supply voltage circuit. The fuel pump fuse supplies power to fuel pump. Disconnecting the fuel pump in-line harness connector isolates the fuel pump supply voltage circuit.
15. This step jumps the fuel pump relay in order to activate the fuel pump.
16. This step tests for an open in the fuel pump feed circuit between the in-line connector and the fuel pump relay.
17. This step tests for an open or high resistance in the fuel pump ground circuit.
20. 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.