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Electronic Control Unit

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Five Easy Steps to Installing a New ECU

While your car isn't a highly advanced machine like the ones from science fiction movies, it does have an on-board computer called the Electronic Control Unit (ECU). Even though it's only a small device, it will seem like the world's ending when it malfunctions because your engine will not start even if your spark plugs and fuel pumps work and you don't see any trouble codes or the "check engine" light. This is because your ECU takes information from your input sensors to govern your car's various systems. It determines the optimum settings for your fuel injectors, ignition times, fuel pumps, idle speed controllers, and air conditioners among other things. When this rare apocalypse does happen, don't panic because you can install a new unit yourself with a few tools, some patience, and a bit of your time.

Required skill level: Novice

Tools and materials needed:

  • new electronic control unit
  • socket wrench
  • screwdriver
  • Discover your ECU's location

    The actual location of your ECU will depend on your car's make, model, and year. Check with your manual or your dealer because you can spend an entire day just looking for an inch-thick metal box that's around six to eight inches long and four to six inches wide. Yours could be behind the interior kick panel trim pieces, dashboard, glove box, or center console. It could also be under the hood or one of the front seats; or it could be mounted on the firewall or inner fender. If your ECU is inside, you'll need to adjust your front seats so you can gain easier access to it before proceeding to the next step.

    Ensure your safety

    Because this is an electronic device, you need to make sure that power isn't running through it so you aren't electrocuted. Take the key out of the ignition and use a socket wrench to disconnect the ground cable from the battery

    Get to the old one

    Take off the parts that obstruct your ECU. This can be as simple as lifting a lid or it can be as complicated as exposing the floor well. Use a screwdriver to remove your old ECU from its mounting bracket and disconnect it from its thick wires.

    Install the new ECU

    Connect your car to your new ECU unit by plugging the wiring harnesses into it, making sure that the plugs are not bent and that the harness is clean and in good condition. Slide it back in place and screw it into the mounting bracket.

    Reversing the process

    Return the parts that cover your ECU into place. Afterwards, reconnect the ground cable to the battery.

    Test to make sure

    Turn your key into the ignition and check to see if all the functions work. If everything seems fine, go on a test drive to ensure that the engine light is off and black smoke doesn't come out of the exhaust. Enjoy it when your car revs up smoothly and idles fine.

    Electronic Control Unit Articles

    • Finding the Better Electronic Control Unit Brand

      Looking for a new computer is a confusing process because there are so many technical jargon, options, and other things that the average Joe has to consider. But that might not be as tricky as buying a new electronic control unit (ECU) for your car because this computer is smaller and there are less obvious features to compare. We've made it easier for you to choose a new ECU by comparing the units from two popular brands: A1 Cardone and AC Delco. Here's what we found:


      You can by car computers in three different conditions: new, remanufactured, or used. A1 Cardone is known for its remanufactured goods. The brand claims that they reverse-engineer ECUs to discover any failed circuit components, which they then change and test several. This means that they have disassembled and inspected the units to identify and replace broken or nearly broken connections to ensure that they meet OEM standards. AC Delco provides remanufactured ECUs as well, but they also have new units to sell. Their new units have been precision-made according to the OEM specifications, meaning it can suit your make well. Providing ECUs in two conditions gives AC Delco its edge.

      WINNER: AC Delco

      Tuning Flexibility

      Just like your computer at home or in the office, car computers need to have their software updated with newer versions or changed with entirely different programs. You should be able to remap the ECU you'll buy in order to get a better performance from your car. Remapping involves using your car's onboard diagnostic port to update your software to get the results you want. AC Delco ECUs are known to be remappable, as they have spawned an online community of "Delco hackers" who can help you when you need to modify your ECU. Meanwhile, A1 Cardone also offers a reprogramming device that can change the brand's ECUs more easily. What's more, several car manufacturers including Ford, Toyota, and GM have validated this reprogrammer so that you're more assured of the compatibility of your car with its software.

      WINNER: A1 Cardone

      Price and product range

      Changing your car's computer is known to be quite expensive. Still, it would be good if you could choose an ECU that suits your car and falls within your budget. AC Delco offers most of its units between $50 and $500 and they have several remanufactured and new units that are between $500 and $800. However, the do have a new ECU that's more than $1,000 in price. Meanwhile, A1 Cardone offers the owners of many different vehicles remanufactured units that are at $600 or much less, making their ECUs the more affordable choice.

      WINNER: A1 Cardone


      Comparing these two brands was a good exercise in helping to determine what to look for in new electronic control units. While AC Delco gave a good fight by offering their units in two different conditions, A1 Cardone seems like the wiser choice because their remanufactured units are more budget-friendly and more easily reprogrammable.