Depends on the type of fault, if one is there. A major fault code (eg. permanent open circuit in something) will keep the light on while you're driving, and it'll keep coming back each time you start the vehicle. A minor code (eg. sensor slightly out of range) might register the lamp to come on once for the duration of a single drive, and might never show up again. However, it will store in memory for a certain period of time and then clear itself. Yeah definitely check/replace plugs, have a good look over everything including filters, make sure all connectors on components are plugged in securely, can't think of much else... good luck with it!