How do you reset the check engine light on a 1999 Pontiac Firebird?

There is no reset for the check engine light. The light is an emissions system malfunction indicator. It is necessary to diagnose and repair the cause. There are aftermarket code readers (an paper clips work too) which will lead you to the area of the problem. After that experience and a good emissions system book is needed to find the real cause. You cannot �just replace� the part the code represents, other emissions systems will cause some codes to set. Skill and knowledge come in play. Take it to a good shop. Disconnect the battery overnight. That will reset the entire computer. It will also reset the fuel learns, takes 100-300 miles to relearn, and will lock the Delco stereo (somewhat permanent if you do not know the code - read the owners manual). If the original condition still exists it will set the code again, otherwise, it will be gone!