what is an ecu

What is an ECU?

The ECU also known as the Electronic Control Unit or as some refer to as “Engine Control Units” (Electronic Control Unit is actual correct term) is a computer within  a vehicle that controls how other components work.  In a nutshell it is a computer with software installed and this software can be removed, changed, upgraded just like any other computer.  It has input sensors where information about the car is sent back to the ECU and output sensors to send information out to the components to tell them how to behave.  If the car was a human, the ECU would be the brain, it has input sensors (nerves) telling the brain information about where our parts of body are, if we are for example in an uncomfortable position etc but also has output sensors to tell the body what to do for example moving our legs into a more comfortable position.  An example of how an ECU operates in a vehicle would be controlling the fuelling into the engine.  The ECU would receive information about how much fuel is entering the chamber of the engine and will send out instructions to reduce it or raise it if it senses it not currently at the correct flow.  These changes all happen in an instant and there are massive number of components on a car being monitored and adjusted all at the same time.  ECUs come in a variety of sizes, shaped and brands.  Some common brands in the UK are:

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Common ECU Brands in the UK


What does an ECU do?

As briefly mentioned above the ECU is a type of computer that controls part of how a vehicle works. There may be more than one ECU in a car controlling different groups of components.  An ECU will receive information from sensors from the parts that it controls like the crankshaft or fuel injection system and then process and store that information.  This information is stored on a memory chip within the ECU. The ECU will then send out signals to those parts it is in charge of controlling telling them to adjust what they are doing.  An example we mentioned above was an ECU receiving information about the amount of fuel going into the chamber of an engine, processing this information, and then sending out a signal to tell the injectors to adjust the amount of fuel. Interestingly people often aren’t aware that there can be multiple ECUs within a vehicle.  There can be an ECU for the traction control/ABS, the lights, movable car body parts for example that are all constantly receiving information, monitoring and controlling our cars. Some cars have multiple ECUs incorporated into one unit known as a “Powertrain Control Module” (PCM).  This is to make it easier to access the ECUs but needs longer wires to reach components that are further away which can sometimes be a disadvantage. .When you hear the description of a Car’s Ecu being “remapped” it in most cases refers to the software that is installed on the ECU that controls the Engine components being modified.  A “Remap” involves the current software (Map) being removed and an upgraded software or “Map” being installed instead. This can then improve car performance as the new programme allows improved control of the car’s engine changing factors such as power or economy etc.

The ECU will have a sticker with a serial number alongside the make.  There are a few ways to identify the model of your ECU.  Most use a search engine and enter the make and serial number but there are also a number of tools online you can use to search the model of your ECU online. If you find that your ECU does not have a sticker, you get your VIN number on your car, call the dealership and ask them for the original part number for the vehicle’s ECU. They will then tell you the correct part number for the ECU you need.  If your ECU is aftermarket and different from OEM (Original Equipment Manufacturer) This route will not work as the dealer will only usually have the ECU part number that the original manufacturer had fitted to the vehicle when it left the factory.

Where can I find my ECU? Where is my ECU located?

Each make and model of car can differ as to where the ECU is located.  Some vehicles have more than one, one may operate other parts of the car rather than the engine.  Each make of car however often keep the ECU in similar places.  Contacting the dealer however and giving them the make, model and year of your car will allow them to tell you where it is located on your car and save you the most time.  Forums are also a good source of finding your ECU location.

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