if its emissions then you'll get engine light, then if its powertrain then it's another code.Then if its brakes you'll get the abs light, there not all the same. When you get an engine light, then it goes off it's an intermittent problem, it might be the climate or the state of climate your driving in, so if it goes out the problem cures itself, and thats why the light goes out. When the light goes out the problem is gone.