My speedometer has been about 10% off since I bought the car. Always has read higher than actual. Yesterday, looked down and the SES light is on, noticed that speedometer is not working. Didnt pull the code, but obviously it will probably be for speedo. Also noticed that now car is idling much higher, around 1000 rpm or so. Are these issues related? Also, am assuming that my cable is probably out, and this is just a matter of replacing it and all will be well. So, as I understand it, hard cable from tranny goes to backside of cluster, where VSS translates speed for ECM to work with....right? I am also assuming that this is probably not a VSS problem, as the speedo would still show movement if cable was intact, right? All of your input is greatly appreciated.

 

Yes, it sounds like the speedo and or cable is shot. The VSS is just a LED emitter and sensor, it counts the "flashes" or beam interruptions as the speedo head turns. So either the cable broke or the speedo is kaput, or both.

 

That is what I was thinking as well. Would that lead to a high idle condition?

 

No, that shouldn't cause a high idle, the IAC might be stuck also.

 

I have a 1991 camaro and should have the VSS and electronic speedo but I have the mechanical one with the plastic gears on it
Does this still do the VSS in the same way?

 

No idea on that one. To check it you can remove the instrument cluster and look on the back side for little yellow box, that is the VSS.