Quote:
Originally Posted by raycow
I am thinking the speed sensor signal is used for other stuff besides the speedometer. It would certainly be needed for the transmission, and possibly also for some of the engine control functions. My guess is that the signal goes to the computer first, and the computer outputs a signal to the speedo. At the very least, you would need some kind of calibration unit between the speedo and the VSS even if nothing else were connected.
Well, I take some of that back. You said 700R4, so no electronics there, assuming this is the transmission that came with the 93 engine, and I honestly don't know if the TBI needs a road speed signal. However, the speedo still a calibration circuit if it is to work from the raw VSS output.
Ok I just now looked at your hand-drawn diagram and the VSS signal definitely goes to the ECM as I suspected. The ECM appears to control the torque converter lockup, so this makes sense. The part that is puzzling me is that there doesn't seem to be any output from the ECM to the speedo. So if you connect the VSS signal directly to the speedo, where is the calibration circuit?
Found it finally. Looking at the hand-drawn diagram again, the VSS does NOT connect directly to the ECM. If you trace the wire from A10, it goes to the "VSS buffer module". I'll bet money that's where the speedo signal comes off. Now your only problem is to find the VSS buffer module.
Ray
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Ray,
I'm not sure I even have this vss buffer module. I wonder if I left it in the donor car? I hooked A10 up to the speedo and it didn't work. I don't know if that is the wrong wire or if I have a bad speedo? back to the drawing board
