Fuel Pump Electrical Circuit Diagnosis

Diagnostic Chart 1 Of 3:

Diagnostic Chart 2 Of 3:

Diagnostic Chart 3 Of 3:

Relay Cavity Identification Table:

Schematic:

CIRCUIT DESCRIPTION
The Powertrain Control Module (PCM) will energize the fuel pump relay for 2 seconds when the ignition switch is turned to the ON position. When the fuel pump relay energizes, the fuel pump will operate and pressurize the fuel system. The fuel pump will continue to operate as long as the PCM is receiving ignition system reference pulses. The fuel pump will stop after 2 seconds if ignition system reference pulses are not detected.

DIAGNOSTIC AIDS
Check for any of the following conditions:
^ Check the resistance of the fuel pump relay. The resistance between terminal 1 and terminal 2 is 79-95 ohms at 20°C (68°F). The resistance between terminal 3 and terminal 4 is infinite.
^ The fuel pump relay's electrical contacts may be pitted or sticking. Replace the fuel pump relay if tapping gently on the relay or wiggling the relay causes a change in the relay's operation.
^ The performance of the fuel pump relay may be affected by temperature. After the vehicle sits outside over-night, run the engine for 30 minutes before you check the fuel pump relay.

A normal fuel pump resistance is 0.8-1.5 ohms at 20°C (68°F).

An intermittent malfunction may be caused by a problem in the fuel pump electrical circuit. Refer to Intermittent Conditions.

Use the relay cavity table in order to locate the correct cavities to probe during diagnosis. The table layout corresponds to the cavity layout of the relay block.

TEST DESCRIPTION
The numbers below refer to the step numbers in the Diagnostic Table.
1. The Powertrain OBD System Check prompts the technician to complete some basic checks, and to save the applicable freeze frame data on the scan tool. This creates an electronic copy of the data that was taken when the fault occurred. The electronic copy can then be referred to for later reference.
2. This step checks if the fuel pump relay can operate the fuel pump. The PCM turns ON the fuel pump relay for 2 seconds when the ignition switch is cycled. Use an assistant in order to operate the ignition switch while you listen for fuel pump operation.
5. This step checks the control circuit of the fuel pump relay.
7. This step determines if the coil side of the fuel pump circuit is operating correctly.
10. This step checks for an electrical fault in the fuel tank or in the fuel pump wire harness.
17. This step determines whether the switched side of the fuel pump relay is always closed.