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Old 05-16-2001, 05:17 PM   #1
subymamma
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Post Does an ECU reset change the way an auto tranny shifts?

I am not sure if your tranny "learns" your driving style or if it's only the fuel mixture that is affected.
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Old 05-16-2001, 05:19 PM   #2
JGard
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no, the shifting of an automatic transmission is all mechanical.
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Old 05-16-2001, 05:21 PM   #3
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Thanks! Wasn't sure if the little computer thingys were liked to the transmission!!
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Old 05-16-2001, 05:25 PM   #4
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Modern automatics are not purely mechanical. They are almost all governed by a computer. This allows them to provide services such as engine braking, and downshifting on throttle-off.

Resetting the ECU probably woudn't have any effect on the TCU, but if you did it by disconnecting the battery, then you would also have reset the TCU.
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Old 05-16-2001, 07:21 PM   #5
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I beg to differ, I recently took my car to the dealer, the auto mirror needed to be changed, and for some reason they took it upon themselvs to reset the ecu by disconecting the battery. I did have a cel because of mods I put on the car. now I 'm waiting for the computer to readjust to the mods. damm
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Old 05-16-2001, 07:48 PM   #6
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I'm definitly not an expert, but I will swear that when I reset the ECU my shift point change on my 00 2.5RS. Isn't the 4EAT a "learning" transmission?
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Old 05-17-2001, 10:42 AM   #7
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I don't understand your point, xtc.
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Old 05-17-2001, 10:50 AM   #8
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hey all...
i did several resets on mine and it does have an affect on your shift points...

the ECU learns how you drive.. and adapts to YOUR driving style...

when someone else would drive my car... it didnt know what the hell was going on cuz i am a red liner and i red lined it a lot...

when you reset the ecu... it has to start over so to speak... now...

i am talkin about a my99 GT... perhaps things have changed since then.. but this is my experience...

j. www.subiegal.com
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Old 05-17-2001, 10:55 AM   #9
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I'm also pretty sure that a ECU/TCU reset will change the way your car shifts. After all, why would it be called an "electronic" auto transmission if it were purely mechanical? Any model year with Subaru's "4EAT" will adapt to your driving style.

A few months ago my car wasn't shifting smoothly from 1st to 2nd (jolting sensation). Simply disconnecting the battery for an hour then letting the car idle for 20 minutes fixed the problem instantly.
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Old 05-17-2001, 08:10 PM   #10
subymamma
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What exactly does ECU and TCU (was that it?) stand for? Let me guess... Electronic Control Unit or something and Transmission Control Unit (or something?).....
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Old 05-17-2001, 08:14 PM   #11
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my point is it changes the shift points.
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Old 05-17-2001, 10:00 PM   #12
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Ok, but does the 4EAT come "preprogrammed" in grandma-mode or do you HAVE to reset the ECU to gain the benefits of this?
i.e. is it always learning, or does it learn "enough" and then stops there? let's say I flog it as much as possible in a week's time - or I get stuck driving in city traffic for whatever amount of time. Does it then adapt and stick with sort of the most recent pattern?
-T

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Old 05-18-2001, 11:12 AM   #13
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ECU = Engine Control Unit (although the proper Subaru term is ECModule)
TCU = I think you got that one right.

There was an article in a past Drive magazine about our learning ECU's. You might be able to find it through Subaru.com or if you have back issues from a year or so ago.

Dennis
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Old 05-18-2001, 11:21 AM   #14
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I agree with subiegal. The ECU learns your driving habits and seems to adjust shift points and fuel/air mixture.

After an ECU reset I notice a huge difference in how/where the car shifts gears.

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Old 05-18-2001, 11:44 AM   #15
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according to my driving habits my car usually shifts around 4500rpm. after a ecu reset i noticed that it shifted really quick for a short time. i would say the ECU has alot to do with the TCU. just wondering but where is the TCU located ? i know the ECU is under the carpet in front of the passenger side.
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