Speedometer issues

mrtohil · Post by **mrtohil** » Thu Aug 14, 2008 11:24 pm

Just wanted to see if anyone's experienced with this issue. I have a '91 GT w/ 5spd manual(muncie). For a long while the speedometer has been inop due to the original VSS being broken(gear driven) and another type of sensor (induction type) put in to plug the hole and that way I can take the original to showand tell to find it. Well, I finally put a new correct type of VSS into the tranny. But the speedmeter does not go past 15mph. The original transmission for this car did have an induction type VSS (this car is on it's third 1.was destroyed by aftermarket clutch 2. was junk trans from salvage 3. currently working fine except for VSS which I broke accidently). I looked in the factory repair manual and it shows both types. I checked the gear on the diff and it seems fine. Does the induction type have a signal amplifier of some sort which is why my speedometer only goes up to 15mph? Could it be a bad new sensor? Could the needle in the cluster be bad from it not working for so long? Idea? Just want to get it working so I can have cruise control again, especially with some long road trips coming up. Thanks.

Post by **Cliff8928** » Fri Aug 15, 2008 2:37 am

The PROM is different in the computer. You currently have the gear driven one? That would explain this situation. The signal is higher from the magnetic VSS and you basically need a different PROM. One from a cavalier would work.

mrtohil · Post by **mrtohil** » Fri Aug 15, 2008 6:47 pm

Hey Cliff, thanks for the reply. I'm assuming by PROM you mean the chip for the engine control mudule? So do I basically try to find a PROM for a '91 Cavalier w/ 3.1L and manual? Or does the transmission option not matter?

mrtohil · Post by **mrtohil** » Fri Aug 15, 2008 7:05 pm

Okay, I'm checking the wiring diagram out now. I see how it's routed, first through the ECM. If I do need a Cavalier Prom, might as well upgrade for the cam I put in.

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