DIY Guide: How to Replace ECM on Subaru – Step-by-Step Tutorial

As a Subaru car owner, you understand how critical the electronic control module (ECM) is to the performance of your vehicle. The ECM acts as the brain of your car’s engine, providing the necessary signals to different components to keep them running seamlessly. When the ECM fails, your car can’t function correctly, or it may not start altogether.

Replacing an ECM is an expensive repair, mainly when done by a mechanic. But did you know that you could replace the ECM yourself? Yes, you heard right! With this DIY guide, you will learn how to replace the ECM in your Subaru car all by yourself. Here is everything you need to know.

What is an ECM, and What Does it Do in Subaru Cars?

An ECM is an electronic control module that manages all the engine’s functions, including fuel injection, ignition, emissions, and other critical systems. Its job is to ensure that every component in the engine works correctly, providing smooth driving, fuel economy, and reliable performance. In Subaru cars, the ECM controls the processes essential for the proper functioning of your car.

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Signs of a Failing ECM

Like any other component in your Subaru car, the ECM is susceptible to wear and tear over time. Here are some telltale signs that your ECM is failing or has failed:

  • The engine light is on, indicating an error code
  • The car won’t start or is stalling
  • Strange noises or vibrations from the engine
  • Unusual behavior of the car’s electrical system

If you experience any of these signs, it is likely that your ECM is failing, and you need to replace it.

Tools Required for Replacing an ECM

Before starting the replacement process, ensure you have the following tools:

  • Wrenches and sockets
  • Screwdrivers
  • Pliers
  • A new ECM

Step-by-Step Guide for Replacing an ECM in a Subaru Car

  1. Disconnect the battery – To ensure your safety, disconnect the car battery. This will prevent electrical surges that could damage the new ECM or other electronic components in your car.

  2. Locate the ECM – The ECM is usually located in the engine bay, right next to the engine. Refer to your car’s manual to determine the exact location of the ECM.

  3. Remove the old ECM – Carefully remove the old ECM by unplugging any connectors and disconnecting any bolts that hold it in place.

  4. Install the new ECM – Place the new ECM in the same position as the old one. Ensure that all connectors are plugged in correctly and any bolts that hold the ECM in place are tightened.

  5. Reconnect the battery – After installing the new ECM, reconnect the car battery.

  6. Clear error codes – Use a scanner to clear any error codes that may have been caused by the failing ECM.

  7. Test the new ECM – Start your car and check that everything is running smoothly. Take your car for a test drive to ensure that it’s performing correctly.

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Common Mistakes to Avoid While Replacing an ECM

  • Not disconnecting the car battery before starting the replacement process
  • Forgetting to clear error codes after installing the new ECM
  • Plugging in connectors incorrectly
  • Not tightening bolts that hold the ECM in place properly

Testing the New ECM

After installing the new ECM, it’s crucial to test it to ensure it’s working correctly. Here are the steps to follow:

  1. Turn the key on and off a few times without starting the car. Listen for any unusual noises.

  2. Start your car and listen for any strange noises or vibrations from the engine.

  3. Take your car for a short test drive to ensure that everything is running smoothly.


Q: Can I replace the ECM in my Subaru car myself?

A: Yes, you can. With this DIY guide, replacing an ECM in your Subaru car should be an easy and straightforward process.

Q: How much does it cost to replace the ECM in a Subaru car?

A: The cost of replacing an ECM in a Subaru car may vary depending on your location and the mechanic you choose. But, on average, expect to pay between $900 and $1,500 for parts and labor.

Q: What happens if I don’t replace a failing ECM in my Subaru car?

A: A failing ECM can cause your engine to fail or not start entirely. Therefore, it’s essential to replace your ECM as soon as you notice any signs of failure.

In conclusion, replacing an ECM in your Subaru car is a simple process that you can carry out by yourself. By following these steps, you can save money and time that would have been spent on a mechanic. Happy repairing!

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Alton Brobst

As a longtime Subaru enthusiast, Alton brings a wealth of knowledge and experience to our blog. From his early days of tinkering with engines to his current role as a certified Subaru technician, Alton has seen it all when it comes to Subarus. When he's not working on cars, he enjoys hiking and exploring the great outdoors.

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