Understanding the working of automobile brainbox

The existence of a brain box in vehicles has been a while, but its advancement in modern automobile keep increasing. It’s used on older cars for controlling a few important components. today almost all parts of modern vehicles are controlled by this device. Today we’ll be discussing the definition, applications, components, diagram, and working of brainbox in vehicles. You’ll also get to know its advantages and disadvantages.

Everything to know about engine control unit (ECU)


What is a brainbox?

An engine control unit or brainbox, which is abbreviated as ECU is a processor that electrically collects data from sensors and uses the collected information to make changes to the engine component. The ECU is programmed to understand the working condition of the vehicle’s components.

So, whenever there are changes in their working, the sensors notify the brainbox so that changes can be made. If a component is faulty, an error notification will be sent to the user, informing them a component has completely broken down. An ECU is also said to be an embedded system in automotive electronics that controls one or more components or sub-systems in vehicles.

brainbox diagram

The system was introduced in the early 1980s, then it was used to control only fuel injections. This is why fuel is precisely injected into internal combustion engines. However, the improvement of electronics and engine design has spread the working function of the brain box or engine control unit to perform almost every operation in cars.

In some automobiles where ECU is not widely used, precisely older ones, a Powertrain Control Module (PCM) is used as a control unit. It generally combines the controls of an Engine Control Unit (ECU) and a Transmission Control Unit (TCU).

The system determines when the gear should be changed, and it controls the system as it back off the throttle making the shift smoother. This PCM was introduced in the late 1970s but was highly recognized in the 1980s together with the electronically controlled carburetors and lockup torque converters.


Below are the applications of brainbox in a vehicle’s various components:

A brainbox is used in vehicles for controlling multiple functions such as cruise control, automatic gear shifting, climate control, engine running, fuel injection/ emission control, cooling system, ignition system, transmission system, charging system, collision avoidance, power mirror, seat & rear mirror controls, etc. in fact, almost all operation in modern vehicles is controlled by the brain box since its components are controlled electronically.

The PCM also senses and monitors various parts in the vehicle such as:

  • Ignition timing, by directing the speed of the firing spark plugs, makes the vehicle’s engine deliver an optimum amount of power per RPM.
  • It monitors the vehicle’s performance using sensors to check the temperature, oil, and fluid level, air intake, emission level, camshaft angle, etc.
  • The PCM also helps to adjust the air-to-gas ratio that’s delivered into the vehicle’s combustion chamber, which results in fuel economy.
  • It ensures the vehicle’s idle speed is not up to an unnecessary RPM.

Diagram of brain box:

brainbox parts

Read more: Everything you need to know about a vehicle electrical system

Working principle

The working of a brainbox is quite easy and can be easily understood. Just as earlier mentioned, the brain box is located at a safer place inside the vehicle. it’s powered by the vehicle’s electrical system, which powers the device as soon as the ignition is on. A sensor is attached to Each functional component of vehicles. this sensor is what sends information to the brain box. they work along with each other with the brain box. This information is what the brainbox uses to change the condition of these components. If the component is faulty, an error notification will be sent to the user.

Watch the video to learn more about how Brainbox works:

Advantages and disadvantages of a brainbox or ECU


Below are the benefits of brain boxes in automobiles:

  • Brainbox is making life easy for drivers.
  • Faulty components are easily detected
  • Automatic control is common with vehicles featuring gearboxes.
  • The engine is properly maintained with the device.
  • Every adjustment is done precisely.
  • The driver receives warning information on bad components.


Despite the advantages of a brainbox, one big limitation still happens. Below are the disadvantages of brain boxes in automobiles:

  • Almost all modern cars use a variety of different sensors to collect the right information and send it to the brain box. The disadvantage of using many different sensors is that they can fail over time which may lead to costly replacements.
  • Access to all functional components is lost if the brain box is faulty.
  • Bad brainboxes or electronic control units can make wrong changes to vehicle parts.

Read more: Understanding automobile air conditioning system


A brain box is a great invention on automotive vehicles as its invention has made life easy for all car users. In this article’ we’ve explained a lot including the definition, functions, application, components, working as well as advantages and disadvantages of a brain box. I hope you enjoyed the reading, if so, kindly comment, share, and recommend this site to other technical students. Thanks!

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