Fuel Pump Electrical Circuit Diagnosis

FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS

CIRCUIT 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
A fuel pump prime terminal is located 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 supply circuit
- An intermittent internal component failure

For an intermittent condition, refer to Testing for Intermittent Conditions and Poor Connections. Intermittent Conditions

TEST DESCRIPTION

Steps 1 - 13:

Steps 14 - 26:

Steps 27 - 28:

The numbers below refer to the step numbers on the diagnostic table.
3. This step determines if the condition is located on the coil side or on the switch side of the fuel pump relay.
4. This step verifies that the powertrain control module (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.
13. This step determines if the condition with the circuit is intermittent.