ECU European Unit, former codename for the now-Euro. An acronym for: http://www.cowan.edu.au/ The ECU or Engine Control Unit is a computer in an automobile which performs engine management tasks, controlling its operation. They are most commonly identified with electronic fuel injection or EFI, which cannot be performed without them. Since the widespread adoption of the OBD-II standard in 1996 the ECU is "officially" referred to as the powertrain control module, or PCM. Duties Depending on the car's capabilities, the ECU may have any of a long list of goals. In the typical car with a limited set of features, the ECU controls fuel delivery, timing advance, and the anti-smog equipment. As RPMs increase, it will increase timing; When the pedal is pressed down significantly further than the current speed would signify, it increases fuel and air delivery in order to provide more speed, and sometimes advances the timing still further to add power. If the knock sensor detects detonation it will retard the timing to preserve the engine. The simplest ECUs (used with carbureted engines) do nothing more than control timing advance and smog equipment for the best possible emissions, and perhaps also fuel delivery; while it is probably possible to make an efficient all-analog emissions control system, the required complexity of such a system makes the computer all but mandatory.