speedometer

[heavyhaulerss]

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..

[HOTROD29335]

what is a speedometer? who uses them

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

[sidman82]

Try all the relays & fuses.

[pdm]

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

What model & year is your truck?

[NotSteve]

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.

[heavyhaulerss]

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..

[mikeymike]

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

[thomasz]

I found that GPS can be a speedo, thanks.

[heavyhaulerss]

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 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.