Engine Fuel Trim

Fuel Trim Diagnosis

Hollenshade's Storefront in Towson MD

Fuel Pump Control Module Diagnosis & Repair

The Fuel Pump Control Module communicates with the Engine Control Module over the vehicle’s Local Area Network. The ECM provides a 5-volt enable signal to the FPCM to enable fuel pump operation. A enable command is also provided initially for 2 seconds when the ignition switch is placed into the RUN position. The fuel pump control module changes the volume of fuel supplied by the fuel pump by varying the duty-cycle of the voltage supplied to the fuel pump. If there is a communication fault on the LAN bus, and the enable signal is still present, the FPCM will default to HIGH-speed fuel pump operation. Actual fuel pump duty cycle is monitored by the FPCM and is reported to the ECM via the LAN bus.

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