Theory of Operation
WARNING: This page is about a different car, the 2011 RAM Cab & Chassis. However, it is still accessible from the selected car via links, so may be relevant.
The Water-In-Fuel (WIF) sensor is attached to the fuel filter. The Powertrain Control Module (PCM) provides a 5-Volt reference signal to the water in fuel sensor. When the water collected in the fuel filter covers the sensor probes, the Water-In-Fuel sensor then pulls the 5-Volt reference voltage low indicating high water accumulation in the fuel filter.