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Old 11-10-2010, 11:58 AM   #1
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Question: Logic behind resetting ECU?

Every car forum I've gone to seems to have a thread on resetting the ECU..and sometimes there is a spate of conflicting information. These questions are for those who actually have the answer rather than guesstimations -- let's make this the real deal shall we?

Q: How does resetting the ECU help? And why should we do so?

Q: If the car does not have any performance modifications, does it make any sense for the car to go back to the baseline? For example: if a car was bought used and the previous owner's driving patterns wildly differ from your own, is there an advantage?


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Old 11-10-2010, 12:03 PM   #2
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I reset my ECU when my engine seized up from taking in water from my CAI, and it worked great after that. It resets the fuel/air ratio. To do it, I disconnected the negative battery terminal for a few minutes, and put it back, and then restarted the car.

Im sure someone else has a better way of explaining it than me, someone, anyone?
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Old 11-10-2010, 12:43 PM   #3
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Basically it makes the car relearn all its settings within its operating environment. This is supposed to help calibrate the computer when weather conditions change such as when rainy seasons make it extra humid or when changing seasons drop ambient temperature like going from fall to winter. Keep in mind that its operating environment isn't limited to just weather but also mechanical changes such as intakes, exhausts, etc. There are sensors in them such as the MAF that affect how the ECU operates.

All in all I do this every time i do my oil change/ clean my air filter. Why? Because it's free. Is it necessary? Probably not. Does it help anything? Maybe. But if your car is accelerating funny or if something isn't quite working as normal (or as in your example buying a used car) you might as well try it. Just make sure you follow the specific procedure for resetting the ECU.
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Old 11-10-2010, 02:27 PM   #4
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^^Which are what?
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Old 11-10-2010, 04:00 PM   #5
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http://www.importtuner.com/powerpage...wrx/index.html

http://www.modified.com/projectcars/...t_1/index.html

two interesting articles where are car is dyno'd before and after ecu resets
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Old 11-10-2010, 04:55 PM   #6
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Our ECU has whats called a "Long Turm Memore" when you clear the ECU it clears all the LTFT (Long Turm Fuel Trim)

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Old 11-10-2010, 05:23 PM   #7
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Quote:
Originally Posted by NotAnSES View Post
I reset my ECU when my engine seized up from taking in water from my CAI, and it worked great after that. It resets the fuel/air ratio. To do it, I disconnected the negative battery terminal for a few minutes, and put it back, and then restarted the car.

Im sure someone else has a better way of explaining it than me, someone, anyone?
Your car hydrolocked and all you did was reset the ECU to get it working? How bad was the seizure?
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Old 11-10-2010, 07:03 PM   #8
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Quote:
Originally Posted by ZX5_Wombat View Post
Basically it makes the car relearn all its settings within its operating environment. This is supposed to help calibrate the computer when weather conditions change such as when rainy seasons make it extra humid or when changing seasons drop ambient temperature like going from fall to winter. Keep in mind that its operating environment isn't limited to just weather but also mechanical changes such as intakes, exhausts, etc. There are sensors in them such as the MAF that affect how the ECU operates.

All in all I do this every time i do my oil change/ clean my air filter. Why? Because it's free. Is it necessary? Probably not. Does it help anything? Maybe. But if your car is accelerating funny or if something isn't quite working as normal (or as in your example buying a used car) you might as well try it. Just make sure you follow the specific procedure for resetting the ECU.
What is the correct procedure to reset the ECU?
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Old 11-10-2010, 07:05 PM   #9
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Quote:
Originally Posted by Buickboy View Post
http://www.importtuner.com/powerpage...wrx/index.html

http://www.modified.com/projectcars/...t_1/index.html

two interesting articles where are car is dyno'd before and after ecu resets
I've read these articles before and while they have great results for the WRX, I wonder what the more immediate effects are for the D23E.
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Old 11-10-2010, 07:07 PM   #10
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Quote:
Originally Posted by 1turbofocus View Post
Our ECU has whats called a "Long Turm Memore" when you clear the ECU it clears all the LTFT (Long Turm Fuel Trim)

Tom

So what is the best way to break a ECU in after the reset? How is the Long Term Fuel Trim best set?
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