The fuel filter assembly has a Water In Fuel (WIF) sensor that controls the operation of a warning lamp in the instrument cluster (refer to Figure 8-30). Like the fuel heater, the WIF sensor receives power through the GAGES fuse when the ignition switch is in the CRANK or RUN position.
When the circuit of the WIF sensor detects that a specific amount of water has accumulated inside the filter assembly, it completes the circuit for the warning lamp by providing a ground path. After the filter is drained of the accumulated water, the WIF sensor opens the warning lamp circuit.
See page 7-20 for details about diagnosing and servicing the WIF sensor.
