For the past three years my speedometer hasn't been working properly. Ussually when starting from a full stop the needle is completely dead. It stays like this until reaching high speeds of 60-70mph approximately. I discovered this recently. I usually drive in town at lower speeds and for the past three years I thought the speedometer was completely gone. Recently, to my surpirse I have been driving on the freeway and discovered that at higher speeds the speedometer works perfectly fine. I can even use my cruise control without any problems. Ok, when it comes alive, the needle is bouncing back and forth +-5mph but then it gets stabilized. Could this be a VSS, speedometer cable problem. If so how can I troubleshoot. Could somebody explain to me how the VSS and speedometer are wired. I have been studying the Haynes and Chilton manuals and it is not very clear. I can't seem to find them in my car. Thanks.

 

Are you generating a VSS error code? If not, the problem is likely in the instrument itself, since the ECM will set the code after a few minutes of driving without a VSS signal

 

wich car? the stick or the auto? I thought the stick still had a nylon driven gear on a speedo cable?

 

I forgot to mention it but yes, i am getting a code 24 which the code for the VSS. My SES light came on a long time ago and set the code but hasn't come on for a long time even though the speedometer has been working as described before. And this is happening in my automatic Z28 LB9 Camnaro not the manual. Could somebody explain to me how the signals work from the VSS, ECM, speedometer cable and cruise control. Where the heck is the speedometer cable and how does it work in conjunction with the VSS sensor.

 

On a '91, there should be no speedometer cable (1986 for Pontiacs). The VSS sends a signal to a buffer module, which splits the signal between the speedometer (completely electric) and ECM.

From your description, the signal from the VSS is a problem, since both the ECM and speedometer are "complaining". It's remotely possible that the buffer module is at fault, but usually the VSS, VSS driven gear, or a connection are at fault. The VSS is mounted on the left side of the transmission: