my speedometer stopped working and i got code 42. i bench tested the speed sensor with a 6 volt battery and it seems to register on the multimeter. the 12 volts and ground wire coming to the speed sensor works. i stuck my finger in where the speed sensor goes and i think i am able to feel a gear in there and the gear turns with the transmission in gear. is that normal? it doesn't seem like it should be moving freely with the trans in gear.

 

ok i stuck a pencil in a drill and put it up against the gear on the speed sensor with it plugged in and had someone look at the speedometer in the truck and it moved. i put the speedometer back in the truck and now the speedometer works. does anyone know if speed sensors fail intermittently? do they need to be taken apart and cleaned?

 

"Intermittent" is how they fail. Someone on this site reported success cleaning one, so it might help.

The sensor has a hall-effect chip; the shaft has a magnet that spins near the chip without touching it. An o-ring keeps transmission oil out of the sensor; if that o-ring fails (particularly if you have metal particles in the oil) that won't help. So if you pull out the shaft, be sure to replace the o-ring as well.

 

well i didn't see an o ring on the shaft. i did see some rubber thing inside the housing that the shaft slides into. i cleaned everything put in some white lithium grease put it back together and it works so far. hopefully it will continue to work.