my speedometer stoped working. I replaced the sensor that screws into the back of trans, & it made no difference. when the speedometer stopped working one time before, the engine would not rev above 1700 with out shaking & missing & I lost a lil horse power, replaced sensor that time & that sloved the problem. now it must be something else. though I have not lost any horse power & trucks revs to 1850 rpms. engine running just fine this time.

what else can I check ? I turned the ign key on & tested the wires that go to the sensor. neither is hot. should one be ? thnak you..

 

what is a speedometer? who uses them

try checking the speed sensor had one go out on my truck a few months ago

 

Try all the relays & fuses.

 

Most speed sensors generate an ac ( alternating current) signal. Neither wire will have power.

What model & year is your truck?

 

I would call a mechanic at the dealership. Most sensors do have a voltage applied to them.

The sensor is really called an inductive transducer. Whenever a metal object passes in front of it, it shorts to ground. This little pulse can be detected by a computer and by timing the length in between each pulse you can determine speed.

I've played with these devices many years ago when I designed an electronic speedometer for my motorcycle. I had the sensor mounted on the swing arm and detected the bolts holding the rear sprocket on as they passed by.

 

Found the problem. kind of... had fault codes looked at & several showed up. also just later yesterday my truck started surging in low gear & almost shut off. from what was diagnosed, it looks like it's a short in the electrical. being a bad ground or a hot grounding out. truck in shop now to reveal the true cause of the problem.my volt meter also starting swinging back & forth. thanks for the input folks..

 

My speedo works on/off whenever it feels like it. Had the sensor replaced and it worked for awhile then started acting up again. Now myGPS is my speedo

 

I found that GPS can be a speedo, thanks.

 

I do know that the speed sensor that screws into back of trans should be bottomed out then backed out 1/2 a turn then tightened.