Fuel Pump Relay: Description and Operation

When the ignition switch is first turned on, and before engaging the starter, the PCM energizes the fuel pump relay which applies power to the fuel pump control module (VIN 1). The PCM sends a signal based on the engine fuel demand to the fuel pump control module in order to to change the control module's voltage output. The fuel pump will then pressurize the fuel system. The fuel pump relay remains on as long as the engine is running or cranking and the PCM is receiving reference pulses. If reference pulses are not present, the PCM de-energizes the fuel pump relay within 2 seconds of the ignition turning on. During high engine load situations the PCM commands the fuel pump to run at high speed. Refer to Fuel Pump Electrical Circuit Diagnosis for further description and diagnosis of the fuel pump electrical circuit.