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How to Reset your ECU System

How to Reset your ECU System

Most cars are intended to drive in different areas of the world, by men and women of different ages, and levels of driving skills. Different car models can operate at different temperature, terrains and altitudes, and they use varying fuels with different purity and octane ratings. That being said, the ECU or Electronic Control Unit of cars is pre-set to suit the requirements of all, and it can be adapted to the individual driving style of its owners. Many people think that they have no control over their vehicle’s ECU system, but that is not the case. This oneHOWTO article will instruct a car owner on how to reset your ECU system, that too without the company noticing it or without damaging your car’s warranty.

You may also be interested in: How to Use a Car Diagnostic Tool
  1. What does the ECU do?
  2. Step by step instructions to reset your ECU system
  3. Another way to reset your ECU system
  4. Drive the car after resetting

What does the ECU do?

First of all, it is important to understand what an ECU system is and what it does in your car. Basically, your car’s ECU system intends to learn about your car’s engine as you drive. In this learning process, the ECU tracks tolerance changes of your car engine’s actuators and sensors. Some of these values are the position of automatic choke while the car is idle, and the injectors’ trim gain as well.

The values that the ECU system learns are stored in the RAM. This RAM is backed-up by a battery, so that it remains saved even when the engine is off. This means that it reads the saved values every time you turn on your engine, and starts from there only, instead of starting from zero. When you decide to reset your ECU system, you intend to clear all the saved logs and long term memory that your ECU system has till date. These logs include idle speed, spark, fuel etc. Trouble codes are also saved in the ECU system for diagnostic purposes. When you reset your ECU, you will set these values to a neutral default, and also clear all the saved trouble codes.

How to Reset your ECU System - What does the ECU do?
Image: cdrperformance.com

Step by step instructions to reset your ECU system

Now that you have made up your mind to reset your ECU system, just follow these instructions and be safe:

  1. Drive your car for around 15 minutes to bring it to its normal operating temperature.
  2. Now stop, open your car’s bonnet and remove the lead of earth from the battery. Make sure that the end of the lead is not in contact with any other metal surface of your car
  3. Wait for 5 minutes.
  4. Depress the brake for around 20 seconds so as to completely discharge the capacitors of the ECU system through brake lights. Now, your ECU system has lost all of its saved memory.
  5. Now, reconnect the lead of earth to the battery and close the bonnet.

The basic step towards resetting the ECU system is to remove the backup power source altogether. To keep the values saved, cars have a fuse that goes right into the battery. Usually, this is the same fuse and line that powers up your radio.

Another way to reset your ECU system

Instead of opening your bonnet and removing the earth lead, you can also disconnect the battery from your car by pulling the fuse that powers up your radio or footlights. You can find this fuse near your fuse box, usually on the lower right hand side of your footlight controls. Follow these step by step instructions for this method:

  1. Pull out your car’s key
  2. Pull out the fuse as well
  3. Wait for 15 seconds and put it back in

This is an easier way of removing any long term memory saved in your car’s ECU system.

How to Reset your ECU System - Another way to reset your ECU system

Drive the car after resetting

Once you have reset your ECU system, it is important to drive the car for around 30 minutes to educate it about your driving style. Whether you are interested in increasing its performance or making your car more flexible and economical, drive it in the same style and your ECU system will adapt to your individual driving style.

If you want to read similar articles to How to Reset your ECU System, we recommend you visit our Car Maintenance and Repair category.

Write a comment
What did you think of this article?
My blazer was starting just fine but the engine was idling high so I took out the ecm fuses to reset it now my 99 blazer is hard to start. Sometimes I have to use starting fluid. Does anyone knows what happened and if I can fix it?
1st there is a way to reset the ECU without disconnecting the battery
2nd The suggestion to drain an ECU internal power source via disconnecting the battery and holding the break pedal down is "fascinating"....
David Post
I have a 1994 fiat Cinqecento......pre obd2
New plugs fitted , plus map sensor and new battery.
The fuel injection light comes on around the same time
Cooling fan kicks in, the engine will not stall, but sounds
Like it's hunting. How can i remove old data on the ECU.
This model has a three pin system conected to thecECU
Having a up and down idle issue 1050-2000rpms on a 05 Nissan Sentra se r 2.5l. I did the relearn steps and nothing. I changed electric throttle body and nothing. I changed cam and crankshaft sensors and nothing. Changed Air Flow sensor and air filter and nothing. In-between the changing of parts I did the relearn steps. only was able to get the relearn to work twice. No codes anymore. Just the up and down idle.
H Wall
want to try this on my new car, what would happen with the radio? will I need to find a code to get it working again?
Dave Flesher
How to set ECU systems on 2.7 Ford ego bost system for more power
Simple to explain to drivers and simple to do.
It worked on my confused Citroen picasso, and the ECU is now operating well, and not giving out strange codes,
OneHowTo Editor
We're so glad we could be of help!
Like the easy way to understand the several ways of resetting the ecu
Image: cdrperformance.com
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How to Reset your ECU System