Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Module, Fuel Pump, Control: Operation
When the Powertrain Control Module (PCM) receives a 'Start' or 'Run' signal, it energizes the Fuel Pump Relay which sends a continuous 12.0 volt supply to the Fuel Pump Control Module (FPCM). Depending on vehicle configuration, the fuel pump relay can be either a removable component or be part of the printed circuit board inside the Power Distribution Center (PDC) and not separately replaceable. The PCM sends commands to the FPCM through a Pulse Width Modulated (PWM) control signal. The FPCM in turn regulates the PWM voltage output to the fuel pump assembly based on inputs from the fuel rail pressure sensor and other engine demands. The PWM signal will vary from 10-100% to maintain the proper fuel pressure in the system. This is a constant pressure fuel system which means any fuel pressure test performed on the fuel pump should show a continuous pressure (regardless of the changes in PWM) The FPCM is a smart device which monitors the fuel pump assembly wiring for circuit faults and reports the faults to the PCM. The PCM receives the feedback from the FPCM through the PWM feedback signal. These faults reported will be stored in the PCM.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.