Theory of Operation
WARNING: This page is about a different car, the 2011 RAM Pickup. 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 bottom of 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. The PCM illuminates the Water In Fuel lamp immediately after the diagnostic runs and fails. During this time water in fuel may cause white smoke, loss of power or hard starting. The Water In Fuel lamp will turn off once the water is drained from the filter.