I've got a code 24 but speedometer works fine, its an 87 2.5 auto and it dies every time you put it in gear or stop. Snap on scanner says no vss signal but speedo works fine. It next says to check or clean vss buffer. I changed the whole instrumert cluster because I couldn't find the buffer,and this cluster didn't change anything. HELP! Thanks!! Oh, I already unhooked the TC switch too, It didnt help anything.

Sounds like your TCC solenoid is stuck. Removing power (disconnecting) from it won't help if it mechanically hung up.

You might get lucky and be able to take it out and clean it. Dirt and trans particles get in there and they hang up. Otherwise, you get to replace it. It in the side cover of the trans.

Also be aware that some of the replacements are wired backwards and won't work until you swap the black and red wires. Compare the new one to the old one before you install it. You notice the red and black wires go to opposite places from the original. I've seen this on three GM replacements.

The VSS buffer is usually used to describe a little box that connects to the mechanical speedo's optical sensor in the back. The Fiero's buffer is built into the speedo. The VSS drives the speedo and the speedo circuit buffers the signal and sends it back to the ECM.

In this case, that ain't your problem. If the VSS signal is dead, the TCC will never lock. In your case it sounds like it's always locked and is stalling the engine.

Terry

[This message has been edited by TK (edited 09-22-2002).]

As terry said... Fiero VSS feeds to the dash then the ECM.

If the dash is working, even after swaping in a good dash, the ECM can't see VSS then the ECM or wiring has some sort of problem.

The VSS "buffer" is in the Fiero dash cluster. It is a separate box in some other GM cars.

Nope, The ECM will not lock the TC if there is a VSS failure. It needs VSS to know when to lock.

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11-Sept-01, The day the world as we knew it ended.

Theogre is right the buffer is solid state and is built into the instrument cluster. It converts the 4000 PPM to 2000 PPM for the ECM why they didn't just make the speedo use 2000 PPM is beyond me. The wire going into the ECM on the 4 cynd. Is dk green as it enters the ECM. If you have an 87 shop manual go to page 8a-80-4. It has a pretty good diagram