If it only works after the car has warmed up, and always when it is warm, then I would suggest the VSS. If it was a bad ground, you could have it coming on anytime, whether the car was warm or not. I say that because if it was a ground or any wire of some sort, it would eventually jiggle around from vibrations in the car to make a connection. Try replacing the VSS, that might be the culprit.
just my thoughts.
AIM: Fiero87311, Snowboarder0311