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ECU repair and replacement

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ECU repair

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What is the ECU of a car?

The Engine Control Unit (ECU) functions as the central nervous system of your car which means it is essential that it is fully functional. The ECU is accountable for controlling key functions of a car engine and allows for optimal engine 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 adjusts to the signals.

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ECU repairs average costs and prices

The cost of ECU repairs can vary depending on your car, but an average cost for ECU work when booked on WhoCanFixMyCar is £232.40.

Below, you can find the average price for a range of popular car makes.

Car MakeAverage Price
Vauxhall£180.59
Peugeot£260.98
Ford£221.54
Mercedes£147.22
BMW£199.66
Volkswagen£365.00

  • ECU repairs

    The average cost of an ECU repair when booked on WhoCanFixMyCar is £175.47.

    The Engine Control Unit acts as a central information system for your car and for you, its driver. It allows you to receive the correct information from your vehicle and enables the engine to run efficiently.

    Can include
    • ECU testing
    • ECU repair
  • Mobile mechanic

    The average cost of a mobile mechanic booked on WhoCanFixMyCar is £62.54.

    A mobile mechanic will visit you at your home or workplace and can carry out a wide range of different repairs. If the repair is more complex, the mechanic will collect your car, take it to a garage to be repaired, and drop it off when it's finished. The exact cost of a mobile mechanic will depend on the repair you need.

    Can include
    • Home visit
    • Servicing
    • Tyre change
    • Oil change
    • Recommended repairs
  • Car diagnostic test

    The average cost of a car diagnostic booked on WhoCanFixMyCar is £48.

    Car diagnostics testing involves plugging your vehicle into special software that can reveal issues with its engine, electrical system, transmission, braking, exhaust system, and more. A specialist will run tests on your vehicle to expose the cause of any problems you're having with your car.

    Can include
    • Full diagnostic testing
    • Recommended repairs

Which ECU service do I need?

There are many reasons why you could have an faulty ECU. If the ECU becomes faulty, your car might run poorly or not run at all. Here are some ECU services that you might need:

ECU testing

There are several steps to ECU testing which will primarily diagnose what is faulty with the car’s ECU. The steps for ECU testing are as follows:

  • An OBD scanner, which is a diagnostic tool, is plugged into the ECU.

  • The OBD will communicate with the ECU and is able to tell a technician a certain fault code. 

  • They will then turn on the car’s ignition

  • Once the car is started, the OBD can extract information from the ECU as the electrical system will be engaged.

  • The technician will cross reference the fault codes

  • The technician will be able to assess what is wrong with the ECU and other potential parts of the car and recommend ECU repairs. 

ECU remapping

Remapping a car – also known as ‘chipping’ – is a quick and fairly cost-effective process that involves adjusting the microchip in your car’s Electronic Control Unit (ECU), to overwrite the manufacturer’s factory settings. This allows your car to function at its full potential.

There are two main reasons for wanting a remap, and they’re known as power and torque. When your car left the factory the car’s maximum performance was intentionally subdued in order to meet product planning objectives or economy and efficiency targets.

We strongly recommend that you only let a qualified specialist remap your car, or else you may end up with damage to the ECU or engine. The cost of remapping your car will vary depending on the stage you require to remap it to and the make and model of your car. 

Top warning signs your ECU need attention

In a modern car, electronic functions are king. Electrical switches, buttons and knobs control virtually every part of your car’s operation in some way. From power windows and door locks to HVAC controls, from immobiliser systems to engine ignition and timing, all that wiring runs through an electronic control unit (ECU) somewhere along the line. Sometimes the ECU will become faulty and there are some common signs to look out for:

Warnings signs that your ECU needs looking at, include: 

1. Intermittent warm starts 

This is when the engine starts up just fine, however, once you arrive at your destination, stop the car, and are ready to drive off again, then your car won’t start up again. This can be quite a common ECU issue which can be repaired by an ECU repair specialist. 

2. Intermittent cold starts

Intermittent cold starts seem to be more common in areas where temperatures tend to be a little more extreme. The problem is similar to intermittent warm starts, however, in this scenario, your vehicle decides it doesn’t want to start and then you try it again an hour or so later and it fires up without delay. The ECU will still need to be repaired in this situation.

3. Water damaged ECU 

If rain has been pouring down rapidly and you suddenly find that your car starts to misfire and run on fewer cylinders producing a rough sound when the engine starts, then this is a common symptom of a water damaged ECU which will need repairing. Some car models are particularly susceptible to this issue because of their design around the ECU housing, which can mean they are sitting in a pool of water due to high water ingress.

4. No throttle response

This is when the vehicle starts up without issue, but when you press the accelerator to set off, nothing happens. This problem can sometimes be accompanied by a warning light on your dashboard. An ECU test is recommended even if you think that it is being caused by an injector fault. This is because an injector fault can cost £1000+ which is considerably more than an ECU test, so it makes sense to get your ECU tested first.

5. If your car just won’t start

An ECU test will help the technician ascertain why this is the case, as numerous reasons can lead to this issue. It can be a problem with the vehicle immobiliser or even if the battery is being cross wired. Taking the car to an ECU repair specialist near you will help eliminate possible parts needing to be looked at. 

6. Decreased performance

If your car feels as though it struggles to go up hills or accelerate down an entrance ramp, it’s possible that your ECU is faulty.

7. Lowered fuel efficiency

Your ECU is partly accountable for managing your vehicle’s fuel to air ratio. Changing this ratio will cause your fuel mileage to suffer.

New ECU costs versus ECU repair

Repairing cost

Repairing Engine Control Units can be performed in a couple of ways. The fastest way is to repair the ECU when there is a problem with the power supply. Sometimes, a skilled ECU mechanic will be able to simply rectify shorts or bad connections. In the rare case that there is a problem with your ECU’s software, you can possibly fix the issue by “flashing” the firmware to reset it to factory specifications.

Replacing cost

The second and more costly option is when there is a bug in the actual software, however this isn’t a widely spread problem. If there is physical damage on your ECU, then you will have to have the ECU replaced. The cost of replacing a ECU can be a few hundred pounds if you drive a very basic car, or well over a thousand pounds if you drive a premium model

Get your ECU repaired at home

If you are looking to get your ECU repaired at home, and looking for a mobile ECU specialist, then the good news is, there are mobile technicians nowadays that perform diagnostic checks and tuning, to car repairs and servicing, all from the customer’s home.

However, if the mobile mechanic finds that your ECU problem needs specialist equipment then they may ask you to take the car to a ECU repair garage near you.

What are some common ECU issues?

If you find any of these warning signs then the ECU may be having issues: 

  • Check engine light is on

  • Engine stalls or misfires

  • Erratic transmission shifts

  • Hard shifts between 1st and 2nd gear

  • Car starts in 3rd gear or other wrong gear

  • Rough, high or erratic idle

  • Vehicle won’t start

  • Vehicle is slow to start

  • Large drop in fuel economy

  • Transmission slips a gear

What happens when my ECU is faulty?

If the ECU has any faults then it may throw off the timing and fuel settings of the engine, which can negatively affect performance. 

How much does an ECU repair cost?

In the majority of cases, the faulty ECU can be repaired or reprogrammed, and this type of repair will usually run between £150 to £750, depending on the make and model of your vehicle.

Does ECU repair come under your warranty?

There may be a chance your ECU repair can be covered under your warranty, but it depends on the manufacturer’s guidelines. Car warranties generally cover the cost of repairs to engines and transmission, fuel systems, air conditioning and cooling systems, gear boxes, steering, suspension, non-frictional clutch and brake parts and electrics. General wear and tear will not be covered. Plus, warranty term lengths differ but a typical example is three years or 60,000 miles – whichever you arrive at first.

Is ECU repair covered by insurance?

The details of your insurance policy will tell you whether ECU repairs are covered and the type of damage it includes. 

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.

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 15,528 mechanics and garages across the UK so we can find competitive ECU repair deals for you.

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