How Long To Leave Battery Disconnected To Reset Car Computer (ECU)?

The ECU is one of the most essential components in your vehicle. It’s responsible for monitoring and controlling all the other systems to make sure that they are working properly. The battery should always be disconnected before work begins on the ECU, but how long should it be disconnected? That depends on your vehicle! This blog post will give and provide a quick overview of what you need to know about disconnecting the battery for various different vehicles.

How long to disconnect battery to reset ECU?

The Electronic Control Unit (ECU) includes different components that are responsible for the regulation of all the engine’s electronic components, including air conditioning, fuel injectors, and spark plugs. The ECU is also responsible for all the functions of the vehicle. The ability of your car‘s ECU to store long-term data in its term memory is one of the most critical features. The engine computers are learning about how you drive your car all the time and will modify the function of other modules as a result. This allows your automobile to operate at its peak performance.

It cannot reset ECU by disconnecting battery for a short time. However, it is required to disconnect and reconnect again for at least 20 minutes before starting up your car’s engine so that all electronic components are fully functional.

Disconnecting the battery will not cause permanent damage to your vehicle’s ECU, but it can cause a change in its functionality. That’s because disconnecting for long enough to reset the processor may make it forget everything that has been learned. These functions can include erasing your programmed radio stations, forgetting previously learned shift points, and your car’s ideal fuel/air mixture. To some car models, there may be changes with their anti-theft system. Because of this, your car will not operate as smoothly as it used to – the engine may sound rougher, and acceleration and gear changes might appear “off.”

How to reset car ECU with battery?

There are simple ways how to reset car computer or vehicle’s ECU.

Disconnecting and reconnecting both car battery terminals is one of the most popular techniques. Allow your vehicle to travel up to 100 miles for all of the computer displays to fully reset. Just remember that removing the negative battery cable can be tricky, but removing it first will ensure that you don’t damage your car. If you start removing the positive cable before the negative, and your wrench may come into touch with any portion of the vehicle, this will result in a short circuit.

You can also reset the ECU through the fuse box. After you’ve completed this procedure, let your automobile sit for at least 10 minutes so that the ECM may re-teach itself with the new modifications.

Resetting the ECU varies depending on which type of car you are driving. To be safe, it is best to check with the owner’s manual, your mechanic, or even your dealership for clear instructions on the specific procedure.

How does resetting car ECU works?

Clearing the ECU’s memory is a process of clearing long-term variables like idle speed, fuel, and spark. It also allows for storing trouble codes that can be used as diagnostic capabilities in case there are any possible problems with your car or truck after it has been turned off.

ECU can also be reprogrammed to increase the performance of your car. But this has to be done with your car dealer/manufacturer to be sure that your car is compatible with the software used.

If you disconnect the battery, will that clear codes?

The battery disconnect technique will work on most automobiles. Some late-model cars will not clear trouble codes by shutting off the battery. Trouble codes are preserved in the ECM’s ROM. The scan tool is the only tool that can clear them and turn off the check engine or malfunction indicator light.


The car’s ECU is the brain of your vehicle. As such, it requires a periodic “reset” to keep running at peak performance and avoid glitches that might lead to breakdowns or other costly repairs down the line.

If you ever encounter this same situation, follow the steps indicated in this article in resetting your car’s ECU. If everything is running smoothly, then you know that ECU has been reset successfully. If the engine is not running properly, you can conclude that there might be a problem with the ECU itself. If this is the issue, it is best to schedule an appointment with your local mechanic as soon as possible so they can further diagnose the problem.

About the author, Phil Borges

Phil Borges is a battery aficionado. He's written extensively about batteries, and he loves nothing more than discussing the latest innovations in the industry. He has a deep understanding of how batteries work, and he's always on the lookout for new ways to improve their performance.