ECU reset question - Subaru WRX Forum
 
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post #1 of 13 Old 01-15-2007, 09:16 PM Thread Starter
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ECU reset question

Forgive me if this is a stupid question. I'm still new to Subaru, and I haven't gotten all the lingo down. My understanding has always been that resetting the ECU was a simple matter of disconnecting the negative battery terminal and draining off any residual charge by depressing the brake pedal. However, I was reading Scoobypedia, and found this:

http://www.scoobypedia.co.uk/index.p...ledge/ECUReset

When referring to "new age" Denso ECUs, they say:

The Denso ECUís donít have a manual reset function like the JECS ones. The Denso units apparently have a non-volatile RAM, so even disconnecting the battery wonít do it. The only way to reset these ECUs is via the OBDII diagnostics port using a computer.

So, I am wondering if I am wrong about resetting the ECU by disconnecting the battery. Now, Scoobypedia does not actually define "new age", and I'm not sure which cars have the Denso ECU. At any rate, I would like to know if my 06 WRX cannot be reset using the battery method. Wehn I bought the SPT intake, I was told by the dealer that disconnecting the battery would *not* reset the ECU. I was skeptical about this in part because of what I have read here and on other forums and also because he told me that the newer models had "hard drives" in the ECUs.

So, what's the real deal? I apologize if this has been covered before. I tried a search, but if you try a search on "ECU reset" you will see why I gave up.

Thanks.

Tim
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post #2 of 13 Old 01-15-2007, 09:31 PM
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Ive done it a few times, by disconnecting the cable hitting the brakes to bleed power and waitning a while and hookin it back up and it works every time.
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post #3 of 13 Old 01-15-2007, 10:25 PM
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If that were true, then any CEL that you had previously would show up again immediately after a reset. I don't believe that information to be entirely correct, however, it may or may not have some correct information.

Considering the fact they call "bugeye" and "blobeye" for "New Age" rather than using MYxx bothers me since it's supposed to be a technical database. I don't mind then throwing the terms around, but that's how it was categorized.

Since it's a site meant to be like wikipedia, it's difficult to know if you can trust the source or the even know who the author really is.

At least on forums you can object to statements and see arguments for validity or even information on the author.

Jon
"We live for a good time, not a long time."
RIP Colin McRae
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post #4 of 13 Old 01-23-2007, 06:59 PM Thread Starter
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I have learned what I think is some important info regarding this. I spoke to a tech at the dealer today while I was picking up my SPT exhaust (see thread in the EJ25T Bolt-on forum). This guy seemed to really know his stuff, so I asked him about the ECU reset. He said that the only way to be sure that the ECU was completely reset was to do it electronically - either with the dealer unit, an AccessPort or one of the open source software systems.

However, he did say that the ECU can be reset by disconnecting the battery, but it takes more than just pressing the brakes for a few seconds. He recommended disconnecting the battery and leaving a door open (dome light on) for 30 minutes to an hour. He also said that the sure way to tell if the ECU is correctly reset is that the engine will not fire up quickly (will require 5 to 10 seconds of cranking) when the battery is reconnected. If it fires right up, the ECU was not completely reset.

I think there might be some truth to this. When I installed my SPT intake, I disconnected the battery and pressed the brake for about 20 seconds, then installed the intake (about 30 minutes). When I reconnected the battery, the car fired right up. I don't think the ECU was completely reset. However, today, when I installed the SPT exhaust, I disconnected the battery, opened the driver door, and left it like that while I let the exhaust cool and installed the new exhaust - total time, about an hour. When I reconnected and went to start the car, it did not start on the first crank (about 5 seconds of cranking) and only started on the second crank after another couple seconds of cranking. If the tech was correct, the ECU was definitely completely reset this time.

Take this for what its worth, but it sounds plausible.

Tim
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post #5 of 13 Old 01-23-2007, 08:51 PM
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I've been a Tech for 10 years now and i conquer with spokeshave. It takes the ecu awhile to rest its self, they started doing this on chrysler's in the mid 90's.
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post #6 of 13 Old 02-25-2007, 12:24 AM
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ecu reset.

don't go through all that. you'll be guessing too much, and might not be able to start the thing. advance autoparts sells an obd ii reader that is able to reset codes for 80 bucks. this is the cheapest one that actually has an option for a reset! quit speculating, crossing your fingers.....blah blah blah. get the right reader and hit the gas. any q's how i did it e-mail at timsgottaride1@yahoo.com
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post #7 of 13 Old 02-25-2007, 10:02 AM
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The disconnecting of the battery and holding down the brake pedal work just fine.If you have alot of electronics in the car (big stereo,radar detector,DVD....) you will have to hold the brake pedal down longer to remove all of the stored up capasitance especially if you have a capasitor for an amp.Try asking that Subaru mechanic if he ever bothered to check the IAM(Ignition Advance Multiplier) after a reset.If the ECU was reset it would have defaulted to 8 on the factory tuning and 12 on a Cobb map.It maxes out at a value of 16

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post #8 of 13 Old 02-25-2007, 07:21 PM Thread Starter
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Quote:
Originally Posted by stim View Post
don't go through all that. you'll be guessing too much, and might not be able to start the thing. advance autoparts sells an obd ii reader that is able to reset codes for 80 bucks. this is the cheapest one that actually has an option for a reset! quit speculating, crossing your fingers.....blah blah blah. get the right reader and hit the gas. any q's how i did it e-mail at timsgottaride1@yahoo.com
I'm not talking about clearing trouble codes, I'm talking about completely resetting the ECU (i.e. completely clearing all volatile memory) to it's "unlearned" state. AFAIK, there is no OBDII reader that will perform an ECU reset. A trouble code is simply a flag in memory. A OBDII code reader can reset the flag for that particular code, but it can't wipe the whole memory. At least I am not aware of any that can. I'm pretty sure that "ECU reset" is not part of the OBDII standard.

At any rate, my point is that simply pressing the brake pedal for a few seconds may not be enough to reset the ECU. For my car, at least, it is obvious whether or not the ECU has been completely reset by how hard it is to crank it up after reset. To get this reset, it takes several minutes of load (dome light works fine). This may not be the case for previous or subsequent years, but I am convinced it is true for my 06 wagon.

Tim
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post #9 of 13 Old 02-26-2007, 07:54 AM
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Quote:
Originally Posted by spokeshave
At any rate, my point is that simply pressing the brake pedal for a few seconds may not be enough to reset the ECU. For my car, at least, it is obvious whether or not the ECU has been completely reset by how hard it is to crank it up after reset. To get this reset, it takes several minutes of load (dome light works fine). This may not be the case for previous or subsequent years, but I am convinced it is true for my 06 wagon.

Tim
I definatly could be different for the 32bit ECU's.I forgot about those.If so the IAM should default to .5 and max out a 1 i believe.Do you use Ecuexplorer at all?

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post #10 of 13 Old 02-26-2007, 12:45 PM
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Quote:
Originally Posted by spokeshave View Post
However, he did say that the ECU can be reset by disconnecting the battery, but it takes more than just pressing the brakes for a few seconds. He recommended disconnecting the battery and leaving a door open (dome light on) for 30 minutes to an hour. Tim
This is what I've been told about airbags. That they can store charge for up to 30 minutes. So when I was installing my alarm on a Honda I disconnected the battery, turned the headlights on and went in ate supper; it can't store power forever.

Last edited by KevinM; 02-26-2007 at 12:45 PM. Reason: typo
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post #11 of 13 Old 02-26-2007, 01:54 PM
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Quote:
Originally Posted by KevinM View Post
This is what I've been told about airbags. That they can store charge for up to 30 minutes. So when I was installing my alarm on a Honda I disconnected the battery, turned the headlights on and went in ate supper; it can't store power forever.
By stepping on the brakes they disapate the charge much,much faster as they pull more wattage.Same concept as turning on your dome light.Hell you can even turn on your hazards and step on the brake. When they stop flashing ,no more stored energy.

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post #12 of 13 Old 03-28-2007, 11:03 PM
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on the same note of the ECU reset i just bought a Black 04 STi with some decent mods on it and the other day driving down the road hit 4th and like a lot of other people had the check engine light come on and the cruise control light flashing... this being my first forced induction vehicle i am thinking crap so i reset the ecu getting gas (disconecting the battery and holding brake) also put the gas cap all the way back on... but the car has had something called ECUTEK done to it will reseting the ECU reset it to stock or will it keep the same settings as before the Reseting? sorry it was really long but if anyone has anything on this
Thanks.
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post #13 of 13 Old 11-15-2007, 12:51 AM
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Scoobypedia

Jon,

I'm the owner of Scoobypedia, my hobby site. I hear your point about 'trusted' material and I'll a have think how I can increase peoples trust in the information. Where I base the information on other published information I link out to and attribute the source. Where I write an article from my own experience I have nothing to cross reference it too like in the case of the page above. I've also [just] added my forum alias' to my Scoobypedia profile page so people can track down my posts everywhere. Let me know if you have other ideas here.

Feedback I've had to date has been very positive, especially so as anyone can correct or amend most articles themselves and see all change history. The idea is basically discuss and argue technical data within the depths of forums (like you are here) and [re]publish what is agreed in a one-stop-shop (like Scoobypedia).

This is what I have done, taken your constructive comments above and updated Scoobypedia to define the horrible terminology used quite extensively in Europe here:

http://www.scoobypedia.co.uk/index.php/Acronyms/NewAge

Doing that makes the ECU reset article clearer I think.

spokeshave,

Back to topic .... the only real way of knowing you have completely reset the ECU is to use a data logger before resetting and note the fault codes (current and historic), IAM and other learned data values e.g. fuel trims. Reset the ECU using what ever method you think you know (electronic is the best/quickest if you have the tools). Before starting the car compare the data values above again. The starting IAM might be different as it varies across MY, domestic market cars and type of tuning company e.g. PPP, EcuTek and is configured in your ECUs ROM. Any fault codes will now be reset as will all learned data.

Again, performing an electronic reset removes all guess work.

Regards,
-Steve.

Quote:
Originally Posted by Vew View Post
If that were true, then any CEL that you had previously would show up again immediately after a reset. I don't believe that information to be entirely correct, however, it may or may not have some correct information.

Considering the fact they call "bugeye" and "blobeye" for "New Age" rather than using MYxx bothers me since it's supposed to be a technical database. I don't mind then throwing the terms around, but that's how it was categorized.

Since it's a site meant to be like wikipedia, it's difficult to know if you can trust the source or the even know who the author really is.

At least on forums you can object to statements and see arguments for validity or even information on the author.
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