Speedometer HELP!!!

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I have a 92 GMC Sonoma V6 4.3 VIN-Z with 700R4 transmission. I recently replaced the motor mounts which of course required that I raise the engine. While doing so, my girlfriends unhooked my speed sensor from the tranny. He hooked it right back up but now it doesn't work. I have tried to reset the computer 2 or 3 times. I have unhooked the battery, the computer, pulled the fuses but nothing seems to work. I now have no cruise controll, no speed, and the odometer doesn't work either. If anyone could inlighten me as to what to do or if you have had the same problem. Someone had said that the dealership may need to reset the computer for me. If anyone knows if this is true on a 92 sonoma that would also be helpful.

posted by  shawnhoggeva1

take it to a gm dealer or a auto shop.

posted by  mustangmann

yeah, headed there today! :thumbs:

posted by  shawnhoggeva1

Well I went to the dealership and they hooked the computer up to it and found that everything in the dash is fine and the wireing, the signal stopped at the transmission. They said that since it was unhooked with power still to it then it possibly caused a short in the VSS (vehicle speed sensor) which is on the transmission. Since that is nothing but a big magnit then it is very easy for something to happen to it. SO if anyone else has this problem then that should be the first thing you check. If you ever unhook your VSS it is possible that you will cause a malfunction.

posted by  shawnhoggeva1

I've got a 1993-94 Pontiac Sunbird that began having speedo problems -- the needle would bounce around, sometimes be correct, sometimes go to zero, sometimes go to the end. I took it to an indie shop, and the mechanic did what your girlfriends did -- I think. However, he replaced the speedo sensor with a new one, first thing -- but not much changed. The speedo ran properly for a few days, but then bounced a few times, and finally quit altogether.

So I brought it back for more work -- the shop says they've done all kinds of tests and can't locate the problem, except that there's no power at the sensor ... so this part of the problem sounds a lot like what you had with your Sonoma, but requiring a different solution.

At any rate, after $300 for the new sensor installation and tests, what I have is a speedo and odo and cruise that don't work at all.

What can go wrong with the magnet on the flywheel in the transmission? Can it fall off the wheel? become de-magnetized? Or is the problem more likely to be electrical elsewhere?

Also, do any of youse have a clue about the bouncing around stuff? I've seen the question on other car forums, but haven't seen any answers at all ...

Thanks -- Phil

posted by  PhilK Phollower

most GM speedometers now are controled by the computer (hence the need for a VSS). if the VSS isnt bad then chances are its is the speedo itself. ive seen this happen a lot (i work at a salvage yard).

posted by  glagon1979

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