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ECU reset

290K views 78 replies 45 participants last post by  zax  
#1 ·
This is how you effectively reset your ECU, after a major power mod or some sort of boost or fueling change/increase i.e. an EBC or AFC:

-Unplug the negative terminal from your battery
-Get in car and pump brake pedal a few times, or until no electrical functions work (tail lights, dashlights, etc)
-let car sit for 45 minutes
-reconnect the negative terminal and take the car for a "spirited" drive, coming as close as possible to redline in each gear (BE SAFE!!!)
-do a cool down drive and make sure you use good gas from then on ;)
 
#4 ·
Of course you let it warm up. Let me rephrase:

Reconnect the battery terminal, drive out of your drive way, let the temperature needle rise to about normal temperature readings, then drive spiritedly.

Come on guys, this is simple...it should go without saying you let your car warm up.
 
#7 ·
I relayed this information more on heresay rather than experience...we needed a stickied ECU reset thread in tutorial, so I made one up based on what I've read over the last 2 years and the search I did before I wrote it. Everyone says let it sit 45 mins. IF you can do it differently and get desired results, by all means....
 
#8 ·
Timdog1650 said:
I relayed this information more on heresay rather than experience...we needed a stickied ECU reset thread in tutorial, so I made one up based on what I've read over the last 2 years and the search I did before I wrote it. Everyone says let it sit 45 mins. IF you can do it differently and get desired results, by all means....
Definately good sticky info:thumbup:
 
#13 ·
the new ap does it for you :thumbup:
 
#14 ·
To clarify, since this is a pretty old thread:

An ECU reset does not require a time period to wait after the battery is disconnected. Just disconnect it, tap the brake pedal, and reconnect it. You are done.

For maximum affect, after resetting, get on a open surface with no traffic, place the car in 3rd gear, increase throttle, and slowly let up on the clutch while brake torquing the car (don't let it move). The object is to increase boost for a time frame of around 5 seconds. This will maximise your ECU settings such that you will immediately gain a good 20 HP over the "worn" stock ECU settings. The background is much more complex than this, but this does work.
 
#15 ·
thanks for the info... i will have to try this now :thumbup:
 
#18 ·
Ditto what was said earlier. The object is to maintain a mid to high steady level of boost for a duration which really can't be achieved unless you are in 5th (or 6th for the STi) and at high rate of speed....and even here the boost is still climbing, which will have an impact on the ecu reset rate.

In short, if you do it right, there is not threat at all to the clutch. In 3rd, it doesn't really put a lot of torque on the drivetrain, but it is low enough for the ECU to quickly allow some boost.

For those with some minor mods...exhaust, etc....you won't believe the difference this makes. It really is noticable.
 
#23 ·
As long as you can maintain positive boost pressure for greater than 5 seconds, it should work. Doing this without breaking will be a bit tough to do, so I guess you could theoretically brake torque the car while it is moving so you don't end up at an excessive rate of speed. I'd try it is 3rd or 4th, starting just below boost RPM (3 grand or so), then start accelrating while applying brake pressure at the same time. For those worried about burning out the clutch, this could be an alternative method.
 
#24 ·
"so I guess you could theoretically brake torque the car while it is moving so you don't end up at an excessive rate of speed"


I'm intrigued as to why you would prefer to load the clutch than the brakes... I would think that the load on the brakes for 5 seconds on a freeway at full boost would cause much less wear than using the clutch and brakes to hold the car stationary at full boost

But I don't know much about it, so perhaps I'm missing something...
 
#25 ·
"so I guess you could theoretically brake torque the car while it is moving so you don't end up at an excessive rate of speed"


I'm intrigued as to why you would prefer to load the clutch than the brakes... I would think that the load on the brakes for 5 seconds on a freeway at full boost would cause much less wear than using the clutch and brakes to hold the car stationary at full boost

But I don't know much about it, so perhaps I'm missing something...
I'm thinking this is getting a bit more complicated that it is. It's simple. Turn car on. Put clutch in. Set E-brake full on. Place in 3rd. Give throttle. Slowly let up on clutch while giving throttle to keep RPMS above 3K/positive boost pressure. Keep clutch slightly out and throttle slightly in for ~ 5 seconds. Done.

There is likely less abuse to the clutch than a normal spirited takeoff. It's over before you know it. Yes, you can also brake torque it while moving, but for me, there is now a safety risk to others when focusing on doing this rather than driving. I'd rather keep it safe and simple right in my own driveway.:thumbup:
 
#27 ·
It is more a "ratio" type increase in HP, so the more your are putting out, the less you will feel it after you reset the ECU. Yes, it still works with stage 1-2 maps, but isn't as noticable when compared to a stock map.

Also..some folks might be forgetting...this happens anytime you reset your ECU eventually anyway...it just takes longer if you let it "learn" on it's own.
 
#29 ·
I just bought an 02 wrx about a month ago. it came with a catback and CAI.

My question is, is it a good idea for me to reset the ECU??:confused: I do not know the history of the car.

If i do reset the ECU, how long will it usually take to learn without doing the 3rd gear trick or breaking?

Thanks for the info! Good write up.:thumbup:
 
#30 · (Edited)
My experience has been that the ECU basically adapts to your driving habits. This has a lot to do with open/closed loop tuning/response which I won't get into right now, but suffice to say, your car "learns" in a non-boost mode, and uses preset set maps once you are into boost.

So, if you drive aggresively after an ECU reset, for the period of time that you drive this way, the car will respond a bit quicker and retain it longer. The intial change would take anywhere from a few days to a few weeks. However, not everyone continuously accelerates hard into boost, every time, every shift, so eventually the ECU will adapt and the car looses some of the edge.

The only time I ever did this was once before a trip to the drag strip, and a few times for non-hp related items associated with maintenance or modifications. I kind of look at it as eventually, it settles back down to it's normal..."all-around" settings where it is good at everything (accel, passing, gas mileage, etc), but no longer has that slightley better kick in the pants feeling the reset gives you.

Also something to consider..the reset lasts about as long as the first set of knock events are recorded. Once that occurs, timing starts getting retarded and the ECU learns that whatever caused the knock to occur is a no-no, and will adjust accordingly. Typically, this will happen on hot days, or if you get a dose of bad gas. Which is why my thoughts have always been that if this is the case, then basically I am sitting on the edge when it comes to ECU tuning parameters every time I reset the ECU. So I ask myself, is this really worth it to me? Not really. Does it really hurt anything? Probably not, but as my daily driver and a father of 4, it just doesn't fit into my overall equation to even go there. For others...shouldn't be an issue at all.

Just so everyone is clear, these are my thoughts and experiences, and certainly should not be taken as gospel, hard-facts. Yours will certainly be different and you should approach how you drive and treat your car accordingly.
 
#31 ·
After my ecu reset, I'm now getting hesitation at 5000rpm every now and then. So much that even my wife noticed it, and she's not too interested in my car behaviour.

After the pause for about 0.5 seconds at 5000rpm, it continues hammering towards the redline as if nothing happened. Quite strange to me...

Has anyone else found this? Is it a common side-effect of the ecu reset?