2005 Pontiac Sunfire....How is the CHECK ENGINE light reset?

It depends on if its a soft or hard reset, If you take both battery cables off of the battery you can touch them together and clear the capacitor in the cars computer. Or take both cables off and let it sit for like 30 min. If you haven't fixed what caused the light to come on in the first place then it will just come back on again after driving it for a while. Some Newer cars have Logs saved in the computer that cant be cleared unless you take it to a dealership and have them put their scan tool on it. Hope this helped.