Fuel Pump Electrical Circuit Diagnosis
FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSISCIRCUIT DESCRIPTION
The control module enables the fuel pump relay when the ignition switch is turned ON. The control module will disable the fuel pump relay within two seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump relay as long as ignition reference pulses are detected. The control module disables the fuel pump relay within two seconds if ignition reference pulses cease to be detected and the ignition remains ON.
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. Intermittent Conditions
TEST DESCRIPTION
Steps 1-6:
Steps 7-12:
Steps 13-16:
Steps 17-21:
Steps 22-29:
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 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.
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.