Does anyone know why it does that? My Check Engine light was just on a couple days ago.. then I went to start up my car today and it wasn't there anymore. I didn't reset the ECU or unplug the battery. Does that mean there's no problem with my car? That's soooo weird!!

 

Sometimes there can be a glitch...such as a Oxygen sensor getting a low O2 reading...or maybe your engine running a little rich making the exhaust read higher emissions or something from bad gas...but as long as the light's off...you should be fine. If it keeps coming on and off...then get it checked out. Hope that helps.

 

Odds are you didn't tighten your gas cap enough one time. One you tighten it enough it takes a few days to go away.