Rodge, how'd you clean the sensor? I just cleaned mine recently as well. I took it out of the housing and just carefully blasted it with contact cleaner. To be honest, it didn't look dirty or built up or anything.
Trac_511, I removed it with a security style torx wrench and sprayed some CRC Electrical Claener on it. Let it dry and replaced it. What ever you do you must not touch the 2 little wires (the actual sensors) on the inside, or the parts dept. will say $300 & change please.