Engine control unit. An engine control unit (ECU), also called an engine control module (ECM), is a device that controls various subsystems of an internal combustion engine. Systems commonly controlled by an ECU include the fuel injection and ignition systems.

The earliest ECUs (used by aircraft engines in the late 1930s) were mechanical-hydraulic units; however, most 21st-century ECUs operate using digital electronics.

Functions 
The main functions of the ECU are typically:
 Fuel injection system
 Ignition system
 Idle speed control (typically either via an idle air control valve or the electronic throttle system)
 Variable valve timing and/or variable valve lift systems

The sensors used by the ECU include:

 accelerator pedal position sensor
 camshaft position sensor
 coolant temperature sensor
 crankshaft position sensor
 knock sensors
 inlet manifold pressure sensor (MAP sensor)
 intake air temperature
 intake air mass flow rate sensor (MAF sensor)
 oxygen (lambda) sensor
 throttle position sensor
 wheel speed sensor

Secondary 
Other functions include:
 Launch control
 Fuel pressure regulator
 Rev limiter
 Wastegate control and anti-lag
 Theft prevention by blocking ignition, in response to input from an immobiliser

In a camless piston engine (an experimental design not currently used in any production vehicles), the ECU has continuous control of when each of the intake and exhaust valves are opened and by how much.

Early systems 
One of the earliest attempts to use such a unitized and automated device to manage multiple engine control functions simultaneously was the  created by BMW in 1939 Kommandogerät system used by the BMW 801 14-cylinder radial engine which powered the Focke-Wulf Fw 190 V5 fighter aircraft. This device replaced the 6 controls used to initiate hard acceleration with one control, however the system could cause surging and stalling problems.

Usage in motor vehicles 
In the early 1970s, the Japanese electronics industry began producing integrated circuits and microcontrollers used for controlling engines. The Ford EEC (Electronic Engine Control) system, which utilized the Toshiba TLCS-12 microprocessor, went into mass production in 1975.

The first Bosch engine management system was the Motronic 1.0, which was introduced in the 1979 BMW 7 Series (E23) This system was based on the existing Bosch Jetronic fuel injection system, to which control of the ignition system was added.

In 1981, a Delco Electronics ECU was used by several Chevrolet and Buick engines to control their fuel system (a closed-loop carburetor) and ignition system. By 1988, Delco Electronics was the leading producer of engine management systems, producing over 28,000 ECUs per day.

Usage in aircraft engines 
Such systems are used for many internal combustion engines in other applications. In aeronautical applications, the systems are known as "FADECs" (Full Authority Digital Engine Controls). This kind of electronic control is less common in piston-engined light fixed-wing aircraft and helicopters than in automobiles. This is due to the common configuration of a carbureted engine with a magneto ignition system that does not require electrical power generated by an alternator to run, which is considered a safety advantage.

See also 
 Air-fuel ratio meter
 Check engine light
 List of auto parts
 On-board diagnostics (OBD)
 Powertrain control module (PCM)

References 

 
Power control
Control unit
Fuel injection systems
Control uni
Onboard computers