Circuit Diagnosis - Fuel Pump Relay

Electrical Diagram:

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, then to the pressure regulator, where the system pressure remains at 380-420 kPa (55-61 psi). Excess fuel returns to the fuel tanks. When the engine is stopped, a scan tool in the output controls can turned 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

The following conditions may have caused the fuel pump fuse to open:

^ The fuse was 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, refer to Symptoms. Testing and Inspection

TEST DESCRIPTION

The numbers below refer to the step numbers on the diagnostic table.

3. For relay terminal identification, refer to the table in the Diagnostic Aids.

5. The test lamp only illuminates for two seconds even though the scan tool commanded position is ON. You will have to command the fuel pump OFF then ON to re-enable the PCM fuel pump control.

12. Inspect the fuel pump fuse for an open. If the fuse is open, check the circuit for a short to ground. Refer to Body and Accessories/ Diagrams.

20. Inspect the fuel pump fuse for an open. If the fuse is open, check the circuit for a short to ground. Refer to Body and Accessories/ Diagrams.