Cummins ISB CM550 (1990-94) Fault Code: 429 PID: 97 SPN: 97 FMI: 4 Water-In-Fuel (WIF) Sensor Circuit

Circuit Description
The WIF sensor is attached to the fuel filter. The WIF sensor sends a signal to the electronic
control module (ECM) when a set volume of water has accumulated in the fuel filter. The WIF
circuit contain two wires: A return ground (pin 20), and a signal wire (pin 40).

Component Location
The water-in-fuel sensor is installed in the fuel filter and is located on the side of the head
approximately midway on the engine.