What does the check engine light mean on a 2003 civic?
it usually means the the EGR valve needs to be replaced. If your car is "bucking" on start up then for sure it is the EGR valve.
What about a 2003 gallant does it have a reset button after you change the oil for service engine light?
There is a reason that the check engine light came on. The ECM (engine control module) detects a problem. You can clear the codes with a code scanner but if the problem hasn't been fixed the light will come back on. You need to have the codes read. The codes will help you determine the cause of the check engine light problem. It may be as simple as a loose fuel cap.