Theory Of Operation
WARNING: This page is about a different car, the 2013 RAM 3500 HD and 2013 RAM 2500 HD. However, it is still accessible from the selected car via links, so may be relevant.
There are two Water-In-Fuel (WIF) sensors attached to the two fuel filters. WIF 1 is attached to the fuel filter mounted on the engine. WIF 2 is attached to a 2nd fuel filter that can now be found mounted to the chassis. The Powertrain Control Module (PCM) provides a 5-Volt reference signal to each WIF sensor. When the water collected in the respective fuel filter covers the sensor probes, the sensor then pulls the 5-Volt reference voltage low indicating high water accumulation in that fuel filter.