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
A fuel pump prime terminal is available at the underhood bussed electrical center (UBEC). Refer to the UBEC cover for terminal location.

The following conditions may have caused the fuel pump fuse to open:
^ A faulty fuse
^ An intermittent short in the fuel pump power feed circuit
^ An intermittent internal problem

For an intermittent condition, refer to Symptoms - Computers and Controls Systems Symptom Related Diagnostic Procedures

TEST DESCRIPTION

Fuel Pump Electrical Circuit Diagnosis - Steps 1-6:

Fuel Pump Electrical Circuit Diagnosis - Steps 7-19:

Fuel Pump Electrical Circuit Diagnosis - Steps 20-27:

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 on 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 ground circuit to the fuel pump relay.
6. This step determines if a voltage is constantly being applied to the fuel pump relay.
12. You may need to remove the fuel tank in order to gain access to the fuel pump connector.
13. 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.
15. Use the same amperage fuse in the jumper as is used to protect the fuel pump circuit.
16. You may need to remove the fuel tank in order to gain access to the fuel pump connector.
17. Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.