If car's running fine, in most cases, the check engine light's on due to some faulty sensor (emissions), or vehicle threw a code fm malfunction. If you don't have the means to self-scan, take car to auto parts/auto repair and they can scan for diagnostic codes. Pretty much any/all vehicles are run by computers so without the codes you're shooting in the dark.
06 Cobalt LS (for my daughter)
MSgt, USAF (Retired)