An electronic control unit (ECU) is a small computer like device that controls any or some of the electronic
systems or subsystems in a motor vehicle. The ECU may also be called an electronic control module (ECM), central
control module (CCM), the control unit or the car's computer.
These small computers if combined will make their processing power and memory more powerful than any personal computer
the average person can buy. A durable and powerful system will be required to operate a high end vehicle when practically
everything is operated electronically with some sensors sending information several hundred times every second.
They are now a basic feature on every motor vehicle manufactured in this century but as usual high end vehicles
have taken the use of the electronic control unit to another level, in fact several levels higher.
How an electronic control unit works is receiving information from one or several sensors around the vehicle
and uses the information to make decisions and carry out certain actions in the vehicle. The decisions made by the
ECU is programmed into its memory so if it receives information that one wheel is spinning too fast it has no choice
but to apply brakes and/or reduce the torque to that
wheel to correct it.
The earliest and most common Electronic Control Units are those that are used to operate the electronic aspects of the
engine and you may sometimes see the term Engine Control Unit being used as they
became popular due to the widespread use of fuel injected engines. The ECU
and sensors used to control engine functions are referred to as an engine management system.
Electronics has been used on vehicles for a very long time now but the driver made the decisions. Power windows and
the lights worked via electronic systems but the driver decided when the windows should be adjusted or when to turn the lights
on or off.
Now everything is improved with electronics and the vehicle can make certain decisions for itself. These decisions are more accurate
than they would be if the driver made them. In the previous example the car operates its own brakes to restore
traction without the intervention of the driver and faster than the driver's reflexes would allow him or her to
react. Each wheel can also be braked individually.
Electronic control units are now used to improve every system and/or subsystem on high end vehicles and many of these
high end vehicles have well over fifty ECUs. All of these Electronic Control Units are connected as they rarely ever work in
total isolation making your vehicle a network of small computers.
Imagine if the ECU that controls the brakes or the airbags malfunctioned when they were needed
the most because the car's computers were processing too much info at that point in time or the ECU has completed its lifetime while
the vehicle is still in its prime.
Since an electronic control unit is basically a small computer they are usually located away from heat, excessive vibrations
and moisture. Some of them even have cooling fans to keep them at a workable temperature.
Some ECUs especially those controlling the engine can be re-programmed using specialized software. The electronic control
unit has certainly justified its existence in the entire automotive industry and not just on high end vehicles.