Why is the control unit important in cars

Information about the control unit in the car

Reading out data from the control unit in a car workshop
Photo: ridofranz / Depositphotos.com

Technical development in the automotive industry is rapid. Today, many essential processes are electronically regulated while driving. These controls are carried out by highly complex electronic circuits, the control unit. For example, it controls the anti-lock braking system, the vehicle engine, the fuel gauge, the rev counter and the alarm system. And it enables the vehicle to be located after a theft.

The principle of the control units

All control units operate according to the input-processing-output principle. The abbreviation “EVA principle” often stands for this. The sensors of a vehicle provide the input. They continuously determine data and measured values. And they pass this data on to the control unit. All incoming values ​​are processed there. This means: The control unit compares the actual actual values ​​transmitted by the sensor with stored setpoint values. If these values ​​do not match, this triggers a reaction. The control unit sends a pulse to the automotive parts, which act as an output. These implement the commands from the control unit. The checking and control usually goes unnoticed by the driver. If the target and actual values ​​deviate too much, the system warns the driver with warning lights or acoustic signals. The same thing happens if an automatic comparison is not possible. In addition, the control units record their activities. Appropriately equipped garages can then understand this. This makes it easier for mechanics to locate and eliminate a defect.

The control unit that is responsible for the anti-lock braking system

How a control unit works can be explained using the anti-lock braking system, also known as ABS for short. Each vehicle wheel is equipped with a sensor; In this case, it is wheel speed sensors that continuously send data to the control unit while driving. The target and actual data are compared. In a dangerous situation there will be deviations as soon as the driver initiates emergency braking. The control unit responsible for ABS then electronically and automatically regulates the braking force - on each individual wheel. This a wheel from locking and the vehicle prevents no longer being manageable.

The control unit for the vehicle engine

Whether it is the injection system, air supply, ignition system, turbocharger and other vehicle engine parts, the engine control unit continuously evaluates countless data. It can often be found in the engine compartment or in the vehicle interior in the central on-board electronics. The engine control unit is sensitive during evaluation, but as a motor vehicle part it has to withstand special loads such as large temperature fluctuations, vibrations and contamination such as dust. Overvoltages and undervoltage must not restrict the functionality of the engine control unit. If the engine control unit is damaged, fault diagnosis for the auto repair shop can be a challenge due to the complexity of this vehicle part. For the vehicle owner, on the other hand, tedious troubleshooting can be associated with high costs.

Control units in the vehicle

With every further development in the automotive industry, the number of control units increases. Whether another driver assistance system, a new safety system, vehicle engine, new communication option - each has its own control unit. One vehicle model alone can be equipped with up to 80 control units, such as the Mercedes S-Class.


Control units are highly complex electronic vehicle parts that should therefore be serviced and repaired in a reliable vehicle workshop.

You can find out more about used control units here.

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