ABS light and check engine light or both on, transmission will not shift into overdrive and speedometer does not work

Hi Amanda,

It sounds like the vehicle speed sensor (VSS) has failed. That will cause all of the things you mentioned.

To confirm it, here is a link that explains how to retrieve codes from this vehicle. You don't need a scan tool. All that's needed is a short jumper wire or even a paper clip.

https://www.2carpros.com/articles/buick-cadillac-chevy-gmc-oldsmobile-pontiac-gm-1983-1995-obd1-code-definitions-and-retrieval-method

The VSS is located on the left rear of the transmission. I attached the directions for replacing it. However, don't do anything until you check for codes. That way we can confirm this is the issue.

Take care,

Joe

See pic below.