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What Is An ECU? Electronic Control Unit (ECU) Explained

ECU or Electronic Control Units are one of the most important parts of a vehicle. There are multiple ECUs in a car that operates different features and controls multiple parameters.

What Is An ECU?


Quite simply put ECU is a device that controls all the electronic features in a car. This may range from fuel injection to maintaining perfect cabin temperature to controlling braking and suspension. Some vehicles have multiple ECU controlling different features while some have a single one controlling everything.

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With vehicles having multiple electronic control units, they are divided on what tasks they perform. Some of these types are as follows.

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Types Of ECU

With vehicles having multiple ECU they are divided on what tasks they perform. Some of these types are as follows.

  1. Engine Control Module
    With its sensors, the ECM ensures the amount of fuel and ignition timing necessary to get the most power and economy out of the engine.
  2. Brake Control Module
    Used in vehicles with ABS, the BCM makes sure that the wheels are not skidding and determine when to trigger braking and let go of the brake to ensure the wheels don’t lock up.
  3. Transmission Control Module
    Used on an automatic vehicle, the TCM ensures you get the smoothest shifts possible by assessing the engine RPM and acceleration of the car.
  4. Telematic Control Module
    Another one with the same abbreviation this TCU ensures the car onboard services are up and running. It controls the satellite navigation and Internet and phone connectivity of the vehicle.
  5. Suspension Control Module
    Present in Cars with active suspension systems, the SCM ensures the correct ride height and optimal changes to suspension depending on the driving condition.

How Does An ECU Work?


Working of an ECU is actually not complicated as one might assume. It is an electronic device which has base numbers and parameters filled in its memory. With multiple sensors around a vehicle feeding the ECU data it can manage and control the electronic systems efficiently by giving orders to improve their output.

Let’s take an example of how ECU controls something by looking at how airbags are deployed during an accident.

The car has sensors located around itself called the crash sensors which inform the ECU when a crash has occurred. The ECU then measures the speed of the vehicle when it undergoes accident and then using its onboard memory compares the data of whether it should launch the airbags or not. If the data provides enough reason the ECU deploys the airbags. Note that all this happens in mere milliseconds.

That covers how an ECU works let us take a look at what happens if it is faulty and even worse when it breaks down.

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What happens If An ECU Is Faulty?

A faulty ECU is probably the worst thing for a car. It’ll work but its performance will be heavily affected. You’ll notice sudden drops in fuel economy and jerky gear shifts. The check engine light staying on might mean a lot of possible errors but an ECU fault is one of the major ones.

What Happens If An ECU Is Dead?


The car won’t start at all. The ECU controls the engine ignition so a dead one will not start the car at all. Other features will not work as well but frankly if the engine is dead other features don’t really matter that much.

That covers the brief explanation of the Electronic Control Unit.

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Kartik Rangam
Kartik Rangam
Content Writer at GoMechanic | Loves Writing | Loves Cars | You know where this is heading | Level 12 Meme Lord | EVolution


  1. I totally agree with you. It is necessary to be aware of the status of your ECUs in the vehicle. You can prevent yourself going to the mechanic if you have some information about your current car’s health.

  2. I would like to know,I have recently installed a Julie Emulator in my Daewoo Matiz, I followed the instructions as described, but the car still wouldn’t start, it’s seems to me there’s not enough spark from the distributor and what cause the lost of spark?
    I shall appreciate any helpful hints to solve this problem.

    I thank you.


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