that is true .. there are lots of things that will set the check engine light
very small things to big things

like filling up w/ gas w/ the engine running can set the light
or a crack in the gas cap w/ also

with it not running bad i dontthink it will be the head issue but you can
never tell till the scanner gets hooked up
mine missedpretty good when the head thing happend to ours
good luck