Speedo inop on 92 SE

Ok, I have wrote about this topic before and have had a few replys but I think I might have found the proble... Car is a 92 SE with the 3.3 V6, 123K miles. What it's doing is sometimes the speedo works for a week then nothing but it will work again you just never know when. The VSS was replaced along with a cluster with only 4K miles on it but still the same. The other day when I hit the cruise the speedo jumped so I think it's in that circut. Shortly after it quit working again and I took my foot and tapped the sound deadener under the steering coluum where the cruise control modual sits and it started to work. I have ordered a new one but want to know what you think.. Could this had been the problem all along??

That may be a wiring problem too.

Well that cruise modual didn't work, speedo still funky.. So far none of the shops have found the proble but keep taking my money. Where do I go from here? What if I took a jumper wire from the ECM directly to the speedo wire behind the cluster? Do you think that would work?

Hey alconk,

your ECM has 3 connectors, so take a look at the black connector with 24 pins labeled A-B. Now B-9 terminal of that connector is purple wire B-10 is yellow wire, and both wires are coming from your vss sensor.Then you have B-11 which is dark green wire that goes to the back of you instrument cluster.

So your concern is that sometimes your needle works sometimes not. My guess is that you have intermittent open somewhere or bad connection. What you can do is use your dvom tester set it to continuity test (option where you can hear a beeeeeep sound when black and red lead is touched together. connect black to one end of the purple wire by the vss sensor and the other (red) lead of your tester to the other end of the purple wire by the your ecm (both ends must be disconnected) if you hear a beeep that means that there is no opens in that wire. However you can wiggle that wire at both ends or wherever you can see it to simulate bumpy road and listen for the beep signal. If you hear it sometimes to stop that means you have intermittent open somewhere in that wire. Do the same for all yellow of your VSS sensor and also do it for dark green wire from your ecm to the back of the instrument panel. Wiggle wires if you hear beep signal to stop you know there is open somewhere. However, if you don't have tester go to AZ get that roll of wire it is about 4-5$ and just cut about 2 inches away from all ends of the connectors and simply insert new portion of wires in between just to test it. If I remember the pin for the dark green wire at the back of your instrument panel cluster will be labeled as "J" please do this tests and let me know what your results are. Thx 3100

also good thing to know is that your vss is a permanent magnet that creates ac voltage in a form of pulses, and the voltage and pulses will increase after 3mph. That voltage and pulses are converted by pcm into mph. So you can also test it by disconnecting vss and extending its wires to inside of the car so you can connect it to your dvom (ac) setting and watch for even increase as your car speed increases. Of course speedometer will not work but you will be able to see if there is nice steady increase in voltage as you feel the speed of the car increase.

Very good! This is pretty much what I'll be doing except the VSS wires and the reason being is when my scanner is attached I can drive the car and the mph will read just fine even when the speedo is acting up so that tells me the signal from the VSS to the ECM is fine. I think the problem lies somewhere between the ECM and the cluster. I won't have time until the weekend but I'll let you know.

Do you think this is a wiring roblem or a component problem? My cruise works fine along with the TCC which bridges off that same green wire.

The speedometer needle is moved by the magnetic field of two coils inside of the instrument cluster, now it could be the dark green wire between the ecm and cluster or something with those two coils. I would hit the top of the dashboard several times to see if that would fix the problem, if not then I would install new wire from ecm to the back of J terminal on ipc if that does not work try another ipc from junk yard. Your assumption about the uninterrupted signal from vss to ecm is correct.

so far we have narrowed it down to the ipc or the dark green wire intermittently open, but you said that the IPC was replaced so the only thing left is the dark green wire. So check J terminal behind the ipc for loose connection or just plug in new wire from ecm to j terminal for testing purpose you don't have to hide the wire just test it first if you can install new terminals at both ends of the green wire.

do you have any other problems with the gauges, because if something is shorting inside of the ipc the magnetic field will be obstructed and that could cause variations. Also check all grounds in the engine compartment since bad grounds can create strange problems.

I see that you are not giving up on this problem and that is good, I am the same way so I will try to help as much as I can.


also when you disconnect ipc connector you will see black and white wire connecting to terminal G (that is your ground) cut about two inches away from the connector and connect jumper wire instead to a good ground (this is to eliminate possibility of bad ground or intermittent short to positive somewhere. Also under the hood look for gauges fuse it is a 10A fuse so make sure it is not loose.

Yes this is driving me nuts!! Especially when you are at a stoplight and the needle pegs 120 and back to 0 then back and forth. The rest of the cluster works great as it did in the original cluster. If this works will I need to cut the green wire where I splice into it so it don't backfeed or does it matter? Or just use a scotchlock connector?

No for testing purposes it would be the best if you can cut the green wire at both ends (by ipc and ecm) one inch away that will give you enough length to play with. Why? because if you use that special connector you are bypassing it but what if the green wire is shorting somewhere under the dashboard this will ruin the signal for the bypass wire. You can do it for ground wires only. Not in this case because we are dealing with important signal from ecm. that is 4000 pulses per mile.

Ok but is that green wire only for the cluster? Because the same green wire bridges off for the cruise, rear defog, and TCC. Weird I know so I'm afraid that if I cut it those items will not work. But not for sure?????

on my wire diagram I did not see any splices for green wire, it should be straight wire to ecm....

please email me your diagram to [email protected]
AWESOME!! I'll let you know in a couple days if it works.

Thanks a million!!:)

AWESOME!! I'll let you know in a couple days if it works.

Thanks a million!!:)


I did realize that there is a splice #218 or 220 that leads to cruse control module... you were right I will look deeper into this sorry for false alarm :frown:

Well I ran a new piece of wire from the ECM up to the cluster and now the speedo works great.

So we really did figure it out :)
:icon16:

Yep, the only thing is my cruise don't work now. But I'd rather have the speedo than the cruise anyway, besides it surged anyway...

Yep, the only thing is my cruise don't work now. But I'd rather have the speedo than the cruise anyway, besides it surged anyway...


under the dashboard you will see main wire harness that leads to the left corner of the dashboard (similar area where some GA-s have fuse box inside of the car).
Remove the wiring harness protector what ever it is plastic or tape 4-10 inches away from the main connection that that harness connects to, there you will see splice #218 that I mentioned before, (look for the dark green it will splice into some other wire) so cut that other wire and splice it in to the new wire that you installed. Your cruse control should work if not then the wire between cruse control and the old green wire was creating problems so do the same thing then (splice new wire from the new wire that you recently installed and connect it to the cruse module).