TallEddie

Hello, I am new to the forum. I tried searching to see if this problem has been posted but I have not found anything.

I have a 96 Tacoma 4cyl 5 spd 4x4. The speedometer is not working. It is reading much faster than I am going. For example, if I am going 45, the speedo will read 60, or 80, or sometimes be pegged out past 110. It is always over by different amounts. Sometimes when it is cold out, when I start out in 1st, the speedo will go from 0 to 110 before I shift to 2nd.

After stopping and starting, sometimes it will start working again, sometimes not. Occasionally, when I am driving at a constant speed and the speedo is reading higher than it should, the needle will fall back and start reading the correct speed.

There is no noise comming from the dash, and the needle is not bouncing at all. It is a mechanical speedometer.

I am wondering if it is the instrument cluster or the part that is in the tranny that turns the cable. Any guidance on diagnosing which part is defective would be greatly appreciated.

Ed

BigBallsMcFalls

slap an OBD II scanner on that can read speed, and then you can figure
out where to begin troubleshooting, without wasting time and money


speed is a standard OBD II variable. some scanners can read it. all OBD II vehicles support it

TallEddie

Thanks, I'll give that a try. I don't have a scanner right now, but I am going to pick one up, probably useful to have around. I didn't even think to check the computer since it is a mechanical speedometer I didn't think the computer would know the speed. After some research on OBD II I now know that it does!

How does the computer know the vehicle speed? I assume there is a sensor somewhere that the computer uses. If there is a sensor, then why would there still be a mechanical speedometer and not an electronic one?

BigBallsMcFalls

who knows, magic elves.

your rig has a speed sensor anyway that measures
output shaft speed and it can be polled by
the ecu and sent to an OBD II scanner

ecu interprets this as speed and it pretty accurate
if you use the tire size,
rating, and tire pressure
listed on the door panel

not all OBD scanners can read speed, check the specs

LSUfan71

Any resolution to this?

I apologize for reviving an old thread but this is exactly the problem I am having, except my truck is a '96 with the 3.4L V6 and 5spd 2wd.