Fuel Conditioning Module
The fuel conditioning module is located on the right side frame rail and consists of a fuel filter (1), water in fuel sensor and electric fuel priming pump. Fuel from the tank or return line system is drawn through the conditioning module by the fuel injection pump. Some return line fuel from the fuel rail is cycled back through the conditioning module to heat the incoming fuel.
Fuel Filter
The paper filter element traps particles in the fuel that may damage the fuel injection system. A CHANGE FUEL FILTER will appear on the driver information center when a fuel filter change is required. The fuel filter life monitor uses two control paths consistent with driving conditions. The primary control is based on the accumulated fuel burned, and the secondary control is based on the fuel rail deviations and high pressure pump duty cycle. If the fuel has been contaminated with water or other contaminates, the monitor will see erratic system corrections and display the message or warning lamp. If the fuel filter is not changed when the message or warning light is displayed, then a fuel restriction could occur and cause other diagnostics to fail. The filter life monitor does not drive the diagnostics, but is a result of the restriction. You must reset the fuel filter life monitor after each fuel filter change. It will not reset itself. Resetting the filter monitor without changing the filter will cause the fuel filter monitor to be inaccurate until the next fuel filter change and reset.
Water in Fuel Sensor
The Water In Fuel Sensor is located at the bottom of the diesel fuel conditioning module. It is an electrical contact switch that closes when the float arm of the switch rises above the acceptable level of water in the fuel filter. The engine control module (ECM) monitors the voltage on the signal circuit of the water in fuel switch. When the water in fuel switch closes the circuit the ECM detects low voltage on the signal circuit and sends a serial data message to the instrument panel cluster to display the WATER IN FUEL SERVICE REQUIRED message.
Fuel Priming Pump
An electric fuel prime pump supplies fuel to low pressure fuel system. The fuel pump is used to prime the fuel system after changing the fuel filter or servicing the fuel system. This fuel pump is powered by the fuel pump relay that is controlled by the engine control module (ECM). The pump is part of the diesel fuel conditioning module assembly. The module assembly is located under the vehicle forward of the fuel tank.