That sensor has very little that can go wrong, just 2 pins that sense the difference in conductivity of water vs diesel fuel. When my WIF function stopped working on my RACOR it had a constant false WIF warning on dash. It turned out to my Racor molded circuit. Being cheap I built a single transistor switch circuit and bypassed the Racor circuit. I looked for the circuit schematic but it must be on an old laptop at home and I am in Cape Breton for the summer. The replacement module is available from Racor if you go that route.