1987, 2.5 and 5 speed.

The speedometer is stuck at 20 MPH, the odometer and the trip does not move. I get a code 24 (speed sensor malfunction) on the scanner. I blocked the car and jack the wheel up and let it run in second gear and using a test light I see there are pulses from the VSS. I try another VSS from an 84 (which I read here is different??) but still nothing working at the speedometer.

I also have read that the speedometer gets it's power from radio circuit, the radio works and I see no blown fuses. Is there any place else I should seek out?

Thanks, John

quote Originally posted by John N: 1987, 2.5 and 5 speed. The speedometer is stuck at 20 MPH, the odometer and the trip does not move. I get a code 24 (speed sensor malfunction) on the scanner. I blocked the car and jack the wheel up and let it run in second gear and using a test light I see there are pulses from the VSS. I try another VSS from an 84 (which I read here is different??) but still nothing working at the speedometer. I also have read that the speedometer gets it's power from radio circuit, the radio works and I see no blown fuses. Is there any place else I should seek out? Thanks, John

check the continuity of all wires between the vss and the ecm. i dont remember if the vss runs into the speedo first, then into the computer or Vice versa, or perhaps it splits and one set of wires goes to the speedo and one to the ecm...... maybe someone else can chime in?? the code 24 usually means the ecm is not seeing the vehicle speed...put a scanner on the computer and see if it reports back the vehicle speed when you are driving around...

Where on the circuit did you run the test light?

You might try disconnecting the speedo connector (it's the one near your left knee that plugs straight up into the bottom of the pod) and re-plugging it in. Sometimes the connectors get a little corroded. If that doesn't work then you might try a continuity check on both the yellow and purple wires between the IP connector and the VSS. The way I'd do that is by simply jumping the two wires together either at the VSS or the IP connector then measuring between the two pins at the other end. Use your mulitmeter set to ohms and you should see zero if the wires are good, and infinite ohms if one of them is broken. If they check out good, then test both wires to see if they're continous to ground (which they shouldn't be) but if they are, then it's a sign that one of them has frayed through the insulation and is shorting out the signal.

quote Originally posted by Bloozberry: Where on the circuit did you run the test light? You might try disconnecting the speedo connector (it's the one near your left knee that plugs straight up into the bottom of the pod) and re-plugging it in. Sometimes the connectors get a little corroded. If that doesn't work then you might try a continuity check on both the yellow and purple wires between the IP connector and the VSS. The way I'd do that is by simply jumping the two wires together either at the VSS or the IP connector then measuring between the two pins at the other end. Use your mulitmeter set to ohms and you should see zero if the wires are good, and infinite ohms if one of them is broken. If they check out good, then test both wires to see if they're continous to ground (which they shouldn't be) but if they are, then it's a sign that one of them has frayed through the insulation and is shorting out the signal.

Well guys you're not going to believe this, after I made this post I was in the garage tying to decided on how I was going to start tracking wires to figure this out and watching/hoping for any replies here. I checked my email from my phone and after reading what Bloozeberry suggested, I thought what the heck, that's an easy thing to check.

So I take off the cover under the dash and what do I find? The darn plug/cable wasn't even connected to the bottom of the instrument panel, it was in fact draped around the steering column.

I don't know if someone unplugged it on purpose so it wouldn't hit the 100,000 mile mark (it stopped working at 97,150 miles) or there were under the dash for some other reason. What ever it was, I plugged it back in and and turn on the ignition switch and the speedo went back to zero and it worked perfect and even the shift light works now!

Thanks for the help here, I was scared it was going to be a real PITA, but turned out to be a very very simple fix.

John N.

Good from your part saying what the problem was .
And Bloozberry is a real good help on this forum , thanks .

[This message has been edited by Robert 2 (edited 03-19-2011).]