Possibly a better title is Engine Management but the term Electronic Fuel Injection or 'EFI' is most familiar to motorists even if that's all they know about it.

Like many other things in the automotive service and repair industry there is a lot of confusion and misinformation about it in terms of what it does, what goes wrong with it and maybe it costs a fortune to fix.

Engine management is generally speaking an engine control system that operates actuators such as injectors and ignition coils based on interpreting information received from various sensors on the engine such as air flow and engine temperature.  Current engine management systems also control the ignition system, cooling system and even an automatic transmission if fitted.  Hence the name EFI or fuel injection is slowly disappearing and the current systems are referred to as Engine Management or possibly more accurately Power Train Control.

Central to it all is the control unit which is a computer and like your PC is programmed to undertake various tasks in response to the drivers commands and various sensors.  The control unit is often called an ECU (electronic control unit) and to add to the mystery is often coloured black!  The ECU can be connected to another computer for diagnostic purposes and unfortuanltly may give the impression to many motorists that any problem can be quickly and easily dioagnosed.  Whilst this is a great place to start when hunting down faults, interpretation of the results and futher specific testing is required in order to effectively repair a fault.  If for example a sensor plug becomes dislodged then the ECU will correctly record a fault with that sensor.  It is really recording a fault on that sensors circuit and will not know that the specific problem is that the plug has came adrift for example.