Fuel Pump Electrical Circuit Diagnosis

Diagnostic Chart (Part 1 Of 3):

Diagnostic Chart (Part 2 of 3):

Diagnostic Chart (Part 3 Of 3):

CIRCUIT DESCRIPTION
The PCM controls the fuel pump relay using a high side driver within the PCM. When the ignition switch is first turned ON, the PCM turns the fuel pump relay ON for 2 seconds. The relay contacts close to apply a fused battery voltage to the fuel pump. The 2 second ON time allows the fuel pump to prime the fuel rail assembly.

DIAGNOSTIC AIDS
The fuel pump can be turned ON using the Special Functions, Engine Output Controls selection on the scan tool.

An intermittent may be caused by a poor connection, rubbed through wire insulation, or a wire broken inside of the insulation. Check for the following conditions:

TEST DESCRIPTION
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.
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.