What is an ECU?
The ECU is responsible for ensuring that the engine in your car is running at its optimal performance. There are a huge number of sensors in your car engine which are critical in reporting how your engine is running as they feed information back to the ECU which in turn makes adjustments.
The first and primary operation of the ECU is power management. The voltages are regulated as most ECU’s have sophisticated power management due to the variety of electrical components operating within a car engine.
One variable controlled by the ECU is the Air/Fuel Ratio. Every engine needs oxygen to works as they are powered using combustion. Therefore, it is essential that the correct amount of air gets into the engine when it needs it. This is also true of fuel injection, if the engine requires more fuel at a higher rate, the rate in which fuel is delivered needs to be higher. This is where the ECU comes into play. When you accelerate, the ECU will deliver a higher amount of fuel and air into the engine.
It is an essential function which is vital for allowing an engine to operate properly.
There are a huge number of functions like this which are come under the supervision of the ECU. This example highlights how important it is to the performance of your car and this is simply one of the many functions performed by the ECU.
For more information on what the ECU is in control of, you can read our dedicated blog post; What is ECU repair?
There are several steps to ECU testing;
- OBD Scanner Plugged in
The OBD scanner is a diagnostic tool which plugs into the ECU. The OBD will communicate with the ECU and is able to tell a technician a certain code. The mechanic looking at your car will plug this into the ECU to begin with.
- Turn on the car’s ignition
Once the car is started, the OBD can talk to the ECU as the electrical system will be engaged.
- Wait for the fault codes to appear
Once the ignition has been turned on, it should only be a matter of moments before the OBD scanner displays a number of codes and the word ‘trouble’ alongside a few.
- Cross reference the fault codes
Once the codes are on show, the mechanic will be able to assess what is wrong with the ECU and other potential parts of the car.
Common ECU Repairs
There are a multitude of reasons for the check engine light to come on and one of them may be a faulty ECU.
The ‘Check Engine’ light has come on
As soon as the engine management light comes on it’s important to take your car for a service, make sure that the ECU is checked during the test as some garages may not decide to carry it out.
The Car won’t start
If your car won’t start you may have a dead battery, faulty electrics or a damaged ECU. If the problem is not electrical then it is highly likely that the ECU is the part causing the issue. By calling a mobile mechanic out to your car you will be able to diagnose the problem quicker than getting your car towed to a garage in your local area.
Other ECU problems
If there is a noticeable drop in the performance of your engine or drop in fuel economy this will likely be caused by the ECU or the on-board computer. It’s important to keep an eye on the rate that you use fuel as well as listening out for the tone of the engine changing as this can be an indicator of an issue caused by a faulty ECU.
The ECU is an expensive component and so having it repaired or replaced could set you back depending on the extent of the damage. An ECU can often be reprogrammed as usually the fault lies in the settings.
The main purpose of remapping an ECU is to change the performance of the engine. The ECU controls key functions carried out by the engine automatically. By altering the flow of air into an engine, or speeding up the injection of fuel the performance of the car will change. Drivers often want to have their ECU remapped to improve the performance of their engine or adjust it so their car can handle specific road conditions.
How long does it take to remap a car?
It does not take longer than an hour to remap a car. The process is relatively simple for a trained mechanic to undertake and there is very little labour work involved with carrying out the service.
What does it mean to reflash an ECU?
Reflashing an ECU is the same as Remapping an ECU. You may also see the term ECU chipping and this is also the same process as remapping.
ECU repair cost
There is good news and bad news.
To replace an entire ECU unit it will cost you thousands, it may be less from car to car depending on the model however the cost of replacing the unit may be more than the value of the car itself.
However the ECU can also be repaired by simply reprogramming the settings which may only cost you around £150.
Where can I get ECU Remapping?
Finding a mechanic you can trust to do a good job and charge a fair price, is not always easy, which is why we've simplified the process.
We work with a network of 11,114 mechanics and garages across the UK so we can find competitive ECU repair deals for you.
To find the best ECU service available in your local area;
- Enter your car registration number
- Give us a few details about your car and your requirements
- We’ll send you a great selection of quotes from mechanics and garages in your local area
You can then compare the quotes and read reviews from previous customers to find the best deal in your local area, before booking the ECU repair online.