Engine Control Unit
Controls various aspects of an internal combustion engine’s operation. ECUs control the quantity of fuel injected into each cylinder, with each engine cycle, by monitoring the engine through sensors. ECUs also control ignition timing and other peripherals. A special category of ECUs are those which are programmable. These units do not have a fixed behavior, but can be reprogrammed by the user. Most ECU's feature a rev limiter. ECU's can also control non-engine functions such as anti-lock braking systems.