Can You Swap ECU from Car to Car? We Explain

The ECU cannot be swapped between cars. This part is programmed for your version of the vehicle and then gets a lot of learning and adjustment along the way. So, your car will just not be working with the used ECU from another car. But some vehicles still allow this. And you can obviously get a new ECU or prepare the used ECU to work in your vehicle.

ECU problems highlights

• Module's importance:Extremely high
• Prone to failure:Yes
• Reasons for failure:Water, damage, software, low voltage, high voltage
• Ways to reset:Cut power, use scanner tool
• Sphere of control:Engine and emissions
• Symptoms of failing:Engine anomalies, CEL light, no start, random warnings
• Price to repair:$150 - $350
• Price to replace:$800 - $1,700

Figuring out what ECU is

Before we see why it's possible or impossible to use the ECU from another car, I should tell you a little about the ECU itself. What's this? Why is it so important for your vehicle? Why can it malfunction?

In simple words, the ECU is the computer that controls almost all units of your car. It gets signals from all sensors and electronic modules, operates them, gives you the needed information on the dash, operates all kinds of solenoids and switches that work automatically. This is the brain of your vehicle.

I will not describe its functions in detail because this would take me a couple of days of writing and you wouldn't read that, anyway. But I will outline some symptoms of the dying ECU.

Here they are:

• your car just glitches - it may not start one day, go crazy when driving, set the wrong RPM when idling, etc.;
• you may find different kinds of error messages every day on the dash of your car;
• diagnosing the problems will be extremely difficult because the ECU itself doesn't have any special codes;
• you may replace anything but the situation will not get better till you replace the ECU.

But when it comes to replacing the ECU, it's like replacing the brain. It's not impossible, in theory, but how can you practically do that? We need to have a deeper look into the process of replacing the ECU and understand why just swapping this part from car to car won't work with modern vehicles and may work well with older ones.

Swapping the ECU - when is it possible?

The ECU is a vital part of the vehicle with port fuel injectors. Older cars had carburetors and they didn't need any special computers to operate the process of combustion, ignition, etc. They used simple technologies and were more reliable in terms of electronics.

Also, older cars fitted with fuel injectors have very simple ECUs that basically have several functions and are not really adjustable. Those ECUs may be swapped without significant changes in how your car works.

But newer vehicles have much more complicated ECUs and swapping is impossible in them because of several important reasons:

• there may be several versions of the ECUs for your engine and you should know which to get;
• very often, different years of your car may have different types of software installed in their computers;
• one vehicle may have different functions of the ECU even in the same year;
• modern ECUs adjust when you use the vehicle and make some changes in their software.

So, if you just take the ECU from a car like yours and install it in your vehicle, you may have problems. First of all, the problem will be with finding the compatible ECU and then you will never know if the computer from another car will actually work with your engine. Sometimes, the same model of the vehicle may have absolutely different types of ECUs in different years.

It doesn't mean that installing the ECU from another car is impossible. I will try to explain how you can do this but you will need to follow some guidelines in order to succeed in such a repair.

New ECU - how to choose and install

The easiest way to repair a car with a broken ECU is to buy the new one. There are usually no aftermarket ECUs, so you will need to buy the OEM one. The only proper way to do this is to go to the dealership, give them the VIN of your vehicle, and they will find the proper ECU for your car.

You may try just installing it and it should work because the ECU the dealership found for you is exactly the same type that was installed in your car by the manufacturer. But still, some adjustments may be needed.

The problem is that the sensors and solenoids adjust to the work of the ECU when you drive your vehicle. So, once you install the new control unit, they may stop working properly. This will lead to a bad start, poor gas mileage, and harsh engine work at first. But after some time, the electronic modules and units will adjust to the new signals and will most likely start working better.

If your vehicle still needs some adjustments, you may go to a good repair shop or to the dealership and have the car inspected by a professional mechanic. Maybe, one or two sensors need to be replaced.

How can you install a used ECU in your car?

To save some money and install the used ECU in your vehicle, you will most likely need to make more steps. First of all, you need to find the proper ECU that was installed in the same model of car with the same type of engine. Sometimes, you will also need the same year because other model years may have different slots and functions.

Here are the steps you will have to make to install the used ECU in your car:

• resetting the old ECU - for this, you will need a good scanner that will help you set the unit to zero settings;
• reset all sensors and solenoids in your vehicle - you better do that while the old ECU is still there;
• installing the new module and adjusting all the software conflicts that could occur;
• using your scanner to carefully see if the new ECU is working correctly and doing its job;
• driving for some time and making more adjustments with the ECU, checking if it works well.

This is just a standard procedure and the bad news is that the labor will cost you a lot. Without professional help, you aren't likely to make all those adjustments and reset everything correctly. When it comes to used ECU, even buying the good one will be a problem for an average driver without the proper skills of a car mechanic.

So, it's not that easy to buy and install the new ECU. But why at all will you need to think about it? Let's see why the ECU may go bad.

What may kill your original ECU?

Like all electronic modules, ECUs in cars are not eternal. Sometimes, you will need to pay attention to them. Although this is not the most unreliable electronic unit in most vehicles, some cars commonly have problems with these parts.

In most cases, the reasons for their failure are as follows:

• bad location and the risk of different destroying factors influencing the ECU;
• water damage which is possible in different cases;
• coolant or oil leaking right onto the ECU under the hood;
• overheating and burning of some elements in the control unit;
• electrical current problems like high voltage and burning of the ECU;
• mechanical damage after a road accident.

I know some vehicles that have their ECUs right over the fender liner. Once the liner is damaged which can happen due to many reasons, water from the road may attack the ECU and kill it. In older Ford Focus vehicles this was one of the common problems.

Also, in some cars, the ECU is placed in such a location that in any minor accident it can be damaged. This leads to huge problems when repairing the vehicle after minor car crashes.

Flooded cars often have issues with ECUs. Even spilled coffee in your car may cause issues with electronics.

Final thoughts

I wouldn't say that replacing the ECU is an easy task for any vehicle. But with modern cars, problems can be unsolvable. Modern ECUs register codes of all sensors, injectors, and even solenoids, and when everything changes, they just won't work. You will need to know how to reset them and prepare for working in new conditions.

If you have problems with the ECU, I recommend going to the dealership or to the repair shop you can trust. A professional mechanic will check the unit and will then tell you what exactly you can do with it. Sometimes, just resetting the old ECU will work well.