I just removed my rocker covers, painted them, replaced the gasket and reinstalled. Took it out for a spin and after about 15 minutes the check engine light came on.

What could this be? Or could it be many many things?

 

I have not had my covers off but i find it hard to believe that was the cause for the light, unless you lost some oil which i doubt you would have lost enough if any. my thoughts are its an unrelated issue, just my opinion