Maddog

Hi people

I have heard of some people reseting the ECU after doing tune up's etc by disconecting the battery for ten minutes,does this work ?
If so what can I expect as a result ?
or is this a risky thing do to ?

kford

I always disconnect the battery for any electrical work e.g. stereo, lights, etc.

I don't know what you're trying to reset, and no it's not risky at all.

3.4v6

for example if you put on an intake on your rig ... the ecu needs to relearn so you disconnect the neg. part of the battery to reset the ecu.

kford

when I did a lot of intake mods (amsoil+Deckplate+ISR) I just pulled the ECU fuse for 15 minutes. But to be honest with you, I'm not sure it did anything.

midiwall

Maddog;

Among other things, the ECU controls timing and fuel delivery to the engine. To do this, it takes a lot of input from the outside, does some funky math, and then makes decisions on how much fuel to stuff at certain airflow rates, etc...

As time goes on (minutes, days, etc) the ECU learns more about how the engine is peforming based on your driving and the various sensor inputs. This allows it to make "better" choices for fuel and timing.

When you change something that will result in one of the ECU inputs reacting differently to the outside world (e.g., deckplate mod will get more air into the engine, hotter plugs will burn fuel differently, supercharger will make you smile..., etc.) then the ECU needs to re-learn how the changes it makes will affect engine performance. To start this learning process, you "reset the ECU". The most assured way of doing this is to pull one of the the negative battery cables (people tend to prefer the negative (black) side) for 10 minutes.

If you don't restart the learning process, then the ECU will be making changes based on what it THOUGHT would happen with your old setup.


When you first start the engine after reseting the ECU, it may run rough or be hard to start. It will quickly start getting better, and then hit about 90% of it's peak performance within 50 miles of driving.

Maddog

Thanks all

im doing a intake mod now so i will reset the ecu as well.

thanks again

slimtim

well when i was workig with imports, same thing goes, u may not feel the difference becase it may not be a large change, but some mods change drasticly, or will chanfge over the next few days, so yes it might not change at all but when re-setting the ecu it eliminates and problems that could accure

Maddog

Its been a couple of days now since i reset my ECU after doing the common air box mod & changing octane (higher) fuel,At first i was doubting if this had made things any better,but in the last 10-15 miles(im trying to not sound like a tourist) ive notice a good improvemnt in smoothness of driving & power.the only thing that bugs me now is that damn wind farm at the front of my motor making all that noise for the 1st Km (opps there i go being a tourist).

Maddog

Its been about 2 or 3 days since i reset my ECU after doing the airbox mod & filled up with higher octane fuel.At first i wasnt so sure that there was any sign of improvement,but in the last 15 odd miles(im trying to not sound like a tourist) it has steadly improved the smoothness & perfomance of my drive.Now the only thing that bugs me is that damn wind farm at the front of my motor ,making all that noise for the 1st km (opp's there i go sounding like a tourist).plus it feels like im driving into a head wind.

Sunday BBQ

Yeah, in the import world, most people would reset the ECU every few weeks or so in order to keep the feeling of their new mods alive. If you were going to the track, then the ECU would be reset in order to achieve the extra horsepower. Basically, after you mod it, the truck will slowly learn what's going on and change the settings as close to stock as possible. So, if you reset it, it kind of like breathing new life into. You probably won't notice it though unless it's pretty pimped out.

MTL_4runner

Just pulling the fuse will only reset the engine ECU and will not reset the tranny after doing any work on it (like a valve body upgrade) or any other systems so the only way to be absolutely sure everything has been reset is to pull the negative on the battery.

midiwall

Ummm, I dunno about that.

It's true that the ECU will learn what's going on, but it's not trying to dumb-down the engine back to stock output. In the case of the deckplate, it's learning about how to get the engine to run smoothly with the additional airflow. If it were trying to return things to stock, then it wouldn't make a lot of sense to add a supercharger or other toys.

Case in point is when I had my truck on a dyno a couple of weeks ago. I've had the deckplate done for well over a year, the last ECU reset was probably 3 months previous and 99% of the time I run with the deckplate out.

My baseline was done with the deckplate in, I then pulled the deckplate and the next run was clearly 6hp up.

mr2bean

hi all,
i dont know if this will help but on my 92 toyota mr2 the 7.5 am efi fuse must be pulled in order to reset the ecu. the battery can be unplugged for 7 days and still hold info and codes if the fuse is left in place. it only takes 10 seconds to clear the ecu via the fuse.
hth
bean

s0nic_strife

Yeah, I was recommended to reset my ECU after I installed my intake.
I let it run for a few days without doing it, then I finaly got off my lazy butt and did it. 100 miles later and I dont really notice anything diffrent.

If its 'learning' wouldnt it learn just the same if I didnt reset it?

midiwall

The process can take a lot longer. It will eventually learn without resetting, but in a change as slight as increasing airflow with a K&N setup or a high-flow air filter then it's better to reset the ECU and let it start from scratch.

For example, say a value that the ECU has learned is "14.2" (random number; not "real" in any sense). If the new value that it will migrate to is "14.7", then because of accumulated data in the ECU, the 5/10th difference will take a long time to approach. But, if you reset the ECU, thus erasing the accumulated data, it will head straight for the new value.


Depending on what you've done to your system, you may not feel a lot of difference. Some folks say that they can feel 2-3hp worth of change, some folks say that's a number that's only really viewable on a dyno. The point being that just 'cause you can't see a night/day tire squealing difference doesn't mean it's not there. Every little bit helps.

pdxyota

My 2005 2.7L 5-speed manual access cab w/ no mods has had issues in 1st gear for a few years: it bogs down every time I start out in 1st gear, like it's having issues w/ fuel injection or something. It had me pretty pissed and I was thinking I'd like to sell the MF because it's so annoying, but I found a link about pulling the negative battery terminal for 10+ minutes to reset the ECU.

I did it 3 days ago and afterward, the truck drives like new. No joke. I wish I'd done it a few years ago. No more hesitation in 1st gear, no more nearly stalling at stop signs, etc. I didn't pull any fuses or anything else, just disconnected the negative wire (actually, I did it for 16 minutes because I got distracted).