Resetting your ECU: After mods and Environment changes.

[mike_sho]

Resetting your ECU. Your ECU is your cars brain. It tells your engine what to do and how to do it based on tons of readings it recieves along with how much throttle is being applied and so on.

After you perform any modification to your car. You should reset your ecu so it can clear its memory and re-learn and adapt to the new parts. Instead of having it try to optimize in with its old parts. Its best to reset and let it learn from the new setup....instead of trying to get it to forget the old.

It can be easily done by unplugging the negative battery cable connection. If I remember correctly my chilton manual says 30 seconds. I still try to leave it off as long as possible. Into the night and possibly next morning if you can.

Then you connect the cable back on. Then start the car outside , let it run till its full warm. Normally 5-10minutes during the summer. Some wait till they hear the fan kick on....but you really just need to see the temp gauge at its normal operation position. Do not touch the gas pedal. Then once warmed.

Shut off and use when you are ready.

Also some like to take the car out and run it hard around 3times. Basically 1st through 3rd like you are racing. Of course this sounds kinda weird , I dont know if to believe this. But it cant hurt and it sounds logical , so it doesnt get some weak run and try to learn from that , you immediatly feed it some hard runs to set it self to and you should be good.

You also have to reset it for every mod. I also do it for every season change. This also lets your car adjust to the environment , different humidites and oxygen levels and densities. All are different variables that can effect your cars performance. So to take full advantage , you again want your car to learn and base its settings off a smaller period of time. So resetting it in lets say winter, its like its whole life was driven in the winter , and so on and so forth. Instead of having it try to adapt from its summer time conditions over to the winter...its best to just start fresh.

-- NOTE , do not try resetting your ecu when you have any sort of fuel additives or things in your car that you wouldnt normally have. So fuel cleaners , higher octane fuel , different fuel than you normally run...dont try this then.

[phathom]

On your 4th gen accords, in the service manual it actually says to reset the ecu undo the backup/radio fuse under the hood. I do the actual ecu one and the backup one just to be safe. just a little info from the Dealership service manual. And it's 10 seconds for that.

[ak47m203]

any reason why?

NOTE , do not try resetting your ecu when you have any sort of fuel additives or things in your car that you wouldnt normally have. So fuel cleaners , higher octane fuel , different fuel than you normally run...dont try this then.

[mike_sho]

Do you run those all the time , no. So you wouldnt want your car tuned on a fuel mixture that isnt going to be used.

[5500]

This is for all manufacturers, or just for HONDA?

[93h22ajspec]

i got a tip when u disconnect the battery go in your car and hold the brake light for 10 secs this will discharge what remaning power u got in your systems so u are sure there is no power and memory is lost

[TOP END MS]

Your ECU stores previous data to make accurate judgements on engine control .. so when you make modifications.. the old data will no longer be accurate to make decissions based on previous data. so what we need to do is clear out the old data and fill it (map it) with new data .. with the new readings coming in ..

I think just removing the 'back-up' fuse in the under hood fuse box for 10 seconds will clear previous CEL codes and reset the ECU .. then let the car idle for about 10 minutes to map out the new readings ..

[flyracerx]

Originally Posted by mike_sho

Do you run those all the time , no. So you wouldnt want your car tuned on a fuel mixture that isnt going to be used.

actually you should reset your ecu when boosting octane. for one reason, ecu's have a memory bank for octane and if you've been using lower octane, the booster won't work too well with the ecu, 'cause the ecu won't boost it's octane "thinking", i guess you could say, as far as the booster boosts your gas.

also, you should reset your ecu periodically after filling up full tank. it can help restore lost power due to ecu adjustments and its octane memory.

[mike_sho]

Originally Posted by 93h22ajspec

i got a tip when u disconnect the battery go in your car and hold the brake light for 10 secs this will discharge what remaning power u got in your systems so u are sure there is no power and memory is lost

Sounds like a good idea, I will try that.

[expierence97]

Is there anything bad that could happen from doing this? or is it pretty safe? It all seems to make sense, just trying to make sure.

[lowridincivic92]

ok so if i were to unhook the neg.- on my battery and let it sit for a while it will reset the ECU??? because i am about to chip it and port and polish the heads on my 92 civic? would it change whp?? up or down?? would it improve acceleration??

[mike_sho]

1. Honda does this almost every single time you come in and get something done under the hood. So, no its NEVER going to hurt the car, its most always going to help the car. Reason why its common practice at Honda.

2. Im not sure if anyone is going to blunty say yeah it makes hp, unless they dyno it. But it makes the car work more properly. Reason why Honda reccomends this in almost every single procedure in the manual.

3. Not sure how much harder it can get. Remove the negative battery cable for 30+ seconds and your honda ECU is now reset. I always try to leave it on as long as humanly possible to ensure a true reset.

[93h22ajspec]

OK The only way to damage your ecu by messing with it would be unpluging it while the battery is still connected both pos and neg... because of the voltage spike when u dicconnect and reconnect could blow stuff in it so always rember to disconnct the battery when unplugging and pluging in your ecu... other than that your safe