Augie

I want the ECM in my bride's 4.2 to get amnesia, so as to study the result of a "This is the first day of the rest of your life." type of electronic epiphany. Can I accomplish this by yanking any (or all three) of the fuses that Audi designates as relating to "engine timing"?

If not, I assume I can physically disconnect the ECM without worrying about electrical rancor.

Is there a need to keep the ECM "dead" for some minimum period of time in order to assure it forgets?

Thanks.

FlyBry2.7T

it's memory capabilities. To remove it's short term memory, the ECM must remain connected, then remove the voltage supply, ie. battery ground. This is the preferred method for American vehicles. Although, I know some Mustang racers that swear by the following: disconnect Both the positive & negative battery cables, hold them together, making contact, then have someone apply the brake pedal several times with the ignition on. Reconnect cables. "Supposedly" this method removes any need for a time delay, ex. disconnect and wait 10 minutes.
Anybody else have any experience?

Augie

...if yanking any fuses will work.

I'm scratching my head about how yanking a battery cable off will look any different to the ECM than pulling its plug, or even yanking appropriate fuses.

2.7tDallas

probably has eveything stored in flash memory - so power doesn't matter

FlyBry2.7T

keep any learned data in a ROM, simply disconnecting the ECM will not erase any learned data, it is stored in memory. Disconnecting the power will remove the stored data, so it will have to learn again. I just don't know if Audi ECM's behave the same. It is mfg. by Bosch, but I don't even know if this means it will behave the same as Porsche, M-B, or BMW ECM's. I need you smart guys out there to verify this.

captainbilly

If you pull the ecu/ecm it may take a while for the voltage in the SRAM memory to drop to zero. I have pulled SRAMs and had them hold their data for several minutes at least. I don't know if the ECM automatically resets it's memory after a power failure, it may or may not, but if you pull the battery cables the power drain from the various computers, radio etc. will quickly pull the system voltage to zero. Unfortunately, pulling the battery cable will also reset all the computers in the car including the radio so you will need to re=input the radio security code. You could pull the ecm plug and put some conductive material across all the pin of the connectors but this might cause some damage if you or the material are at a different potential than the ECM.

After thinking about this for a while I think the safest bet is to disconnect the ECM for a while (I am not real sure how long a while is, probably a few minutes is plenty) and then reconnect. It is possible that even the learned data is in FLASH, in which case nothing but a computer command to erase the data will work. The data for the standard and chipped engine parameters is in FLASH but the learned data probably is not.

Ming 2.7T

Have heard that if you disconnect the battery lead for 15 minutes, then reconnect, the ECU will function at its optimum levels , then it will pull back to normal settings.
Heard that radio needs to be reset, but , I pulled the neg lead off and then reconnected, just to see what happens to radio and such, - radio worked fine, stations were ok. But, the windows lost their one touch capability but that is very easy to correct. Just did it once so,,, others may have found you needed to code radio again.

FlyBry2.7T

Re: captainbilly, how is this affected when the dealership "flashes" the ECM with updates/changes.