ECU (An engine control unit), generally called the (PCM) powertrain control module, is a type of electronic control unit that controls a chain of actuators on an internal combustion engine to make sure the optimum running. It does this by analysis values from a multitude of sensors within the engine bay, interpreting the data using multidimensional performance maps (called lookup tables), and adjusting the engine actuators as a result.
Before ECUs, air/fuel mixture, ignition timing, and inactive speed were mechanically set and dynamically controlled by mechanical and pneumatic means. One of the initial attempts to use such a unitized and automated device to run multiple engine control functions simultaneously was the “Kommandogerät” created by BMW in 1939, for their 801 14-cylinder aviation radial engine. This device replaced the 6 controls used to begin hard acceleration with one control in the 801 series-equipped aircraft. However, it had some problems: it would flow the engine, making close formation flying of the Fw 190 somewhat difficult, and at first it switched supercharger gears unsympathetically and at random, which could throw the aircraft into an extremely dangerous stall or turn.