96 bonnie, transmission control

My 96 bonneville transmission control system triggers my check engine light.
what should I do?
where can I find it?
how can I test it?
and how can I fix/replace it?

Take the car to a transmission shop that has the ability to scan the transmission for problems. If it is truly a problem in the transmission they will be able to diagnose it for you very easily. Most scanners don't have the ability to scan transmissions that is why I recommend a shop.