Vehicles Without Auxiliary Fuel Pump
The Fuel Pump Driver Module (FPDM) is attached to a bracket and secured by two nuts to the right side D-pillar behind the right side seat bolster.
The Low Pressure (LP) fuel pump operation is regulated by the FPDM which is controlled by the Powertrain Control Module (PCM). The FPDM regulates the flow and pressure supplied by controlling the operation of the LP fuel pump using a Pulse Width Modulation (PWM) output.
The FPDM is powered by a supply from the fuel pump relay in the Rear Junction Box (RJB). The LP fuel pump relay is energized on opening the driver's door, pressing the start button only or pressing the start button and the footbrake (which initiates engine cranking). The FPDM supplies power to the LP fuel pump, and adjusts the power to control the speed of the LP fuel pump and the pressure and flow in the fuel delivery line.
A PWM signal from the PCM tells the FPDM the required speed for the fuel pump. The on time of the PWM signal represents half the fuel pump speed, for example; if the PWM signal has an on time of 50%, the FPDM drives the pump at 100%.
The FPDM will only energize the fuel pump if it receives a valid PWM signal, with an on time of between 4% and 50%. To switch the fuel pump off, the PCM transmits a PWM signal with an on time of 75%.
The output pressure from the LP fuel pump will change with changes of engine demand and fuel temperature. The PCM calibrates the engine and fuel demands then sends a PWM signal to the FPDM to adjust the speed of the LP fuel pump as necessary.
If the Restraints Control Module (RCM) outputs a crash signal on the high speed Controller Area Network (CAN) powertrain systems bus, the Body Control Module/Gateway Module (BCM/GWM) assembly de-energizes the fuel pump relay to prevent any further fuel being pumped to the engine.
If the PCM does not detect pressure in the fuel delivery line, it stops, or refuses to start the engine and stores the appropriate Diagnostic Trouble Code (DTC).
The PCM receives a monitoring signal from the FPDM. Any DTC's produced by the FPDM are stored by the PCM.
DTC's can be retrieved from the PCM using an approved diagnostic system. The FPDM itself cannot be interrogated by the approved diagnostic system.