i have a 96 bonneville and the check engine is always on. i just changed my transmission and the engine or oil sensor(dont remember which one). the car runs perfect after the transmission was changed but the check engine light is still on. what are some reasons for this?

You need to find out what code it is throwing. Without knowing why the light is on, there isn't much we can do to help you.

Also, what trim line, etc... is your car? (se, sse, sle, ssei / superncharged or non-supercharged). And where are from? We may have members in your area that can help.