A check engine light is an indicator that a computerized engine-management system uses to indicate a malfunction. Found on the instrument panel of most automobiles, it is typically an amber or red color. The light generally has two stages: steady (indicating a minor fault) and flashing (indicating a severe fault). When the Check Engine Light is lit, the engine control unit stores a fault code related to the malfunction, which can be retrieved—although in many models this requires the use of a scan tool. This warning light can indicate almost anything from a loose gas cap to a serious knock in the engine.