Fuel Pump Electrical Circuit Diagnosis

Schematic:

CIRCUIT DESCRIPTION
When the ignition switch is ON, the PCM activates the in-tank fuel pump. The fuel pump remains ON as long as the PCM receives reference pulses from the ignition system. If there are no reference pulses, the PCM turns the fuel pump OFF after about 2-3 seconds. The pump delivers fuel to the fuel rail and injectors. The fuel pressure regulator, located in the fuel tank, maintains the system pressure at 380-410 kPa (55-60 psi). Excess fuel returns to the fuel tank. When the engine is stopped, a scan tool in the output controls function can turn ON the fuel pump. Improper fuel system pressure results in one or many of the following symptoms:
^ Cranks but will not run
^ Cuts out, may feel like an ignition problem
^ Poor fuel economy
^ Loss of power
^ Hesitation
^ DTCs

DIAGNOSTIC AIDS

IMPORTANT:
^ Remove any debris from the PCM connector surfaces before servicing the PCM. Inspect the PCM connector gaskets when diagnosing/replacing the PCM. Ensure that the gaskets are installed correctly. The gaskets prevent contaminant intrusion into the PCM.
^ For any test that requires probing the PCM or component harness connectors, use the J 35616-A connector test adapter kit. Using this kit prevents any damage to the harness connector terminals. Refer to Using Connector Test Adapters in Diagrams.

For an intermittent, refer to Intermittent Conditions. Intermittent Conditions

TEST DESCRIPTION

Steps 1 - 11:

Steps 12 - 19:

Steps 20 - 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. Verifies that the powertrain control module is providing voltage to the fuel pump relay.
5. 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. This step determines if the condition is between the fuel pump relay and the body pass through connector.
15. This step tests if the relay is causing the condition. Use a fused jumper wire with a 20 Amp fuse.
16. This step determines if the condition is between the fuel pump relay and the body pass through connector.
17. This step verifies if the fuel pump ground circuit is causing the condition. Inspect all connections for corrosion or poor connections.
18. A condition with the fuel pump jumper harness may cause the pump to be inoperative. Inspect the fuel pump jumper harness carefully.
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.