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:
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.