Check Engine - Check engine lights are part of the OBD I (on board diagnostics) system started in 1981 and later OBD II, in 1994 system. It was designed to monitor emission problems and alert drivers of problems. Vehicle computers use input signals from sensors to control signals for spark delivery, fuel, and other related functions that could effect emissions. In later OBD II systems electronic transmission shifting functions and advanced catalytic converter monitoring also came into play. When any of these signals move outside of government mandated limits, the computer turns the check engine light on and in most cases will set a code which can be obtained by using a code reader or more elaborate computer. Engine lights that are blinking represent a more serious problem and the vehicle should be slowed to a stop in a safe area ASAP. A light that comes on and stays on is important but not as critical but you should make an appointment to get your vehicle looked at right away.