A check engine light (Mil Malfunction indicator light) does not necessarily mean that something in the engine will break or is broken and your car will stop. It could be a malfunctioning anti-pollution device witch will not affect your driving but it WILL affect your gas mileage. There is a LOT of reason why an MIL will turn ON suddenly so it could be anything. A ROOM fuse is the fuse for the illumination of the interior of your vehicle (dome-light, trunk-light etc).