Fuel Pump Electrical Circuit Diagnosis

FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS

CIRCUIT DESCRIPTION
When the ignition is turned ON, the powertrain control module (PCM) will turn ON the in-tank fuel pump. The in-tank fuel pump will remain ON as long as the engine is cranking or running and the PCM is receiving reference pulses. If there are no reference pulses, the PCM will turn the in-tank fuel pump OFF 2 seconds after the ignition is turned ON or 2 seconds after the engine stops running.

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:
- The fuse is faulty.
- There is an intermittent short in the fuel pump power feed circuit.
- The fuel pump has an intermittent internal problem.

For an intermittent condition,

TEST DESCRIPTION

Steps 1-13:

Steps 14-25:

Steps 26-27:

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 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. To gain access to the fuel pump connector, the fuel tank may need to be removed.
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. To gain access to the fuel pump connector, the fuel tank may need to be removed.
17. Inspect the ground connection for the fuel pump. Be certain all ground connections are clean and tight.