ECU resetting

[fronton]

Does anyone know how to reset the ECU so it "relearns" your driving style? I was just reading that you need to disconnect the battery then hold the positive and negative cables together for 30 min with the key on. This sounds really odd and makes me nervous about frying something.

Anyone have experience with this in a s38 e30?

[Swanny]

Just unplug the battery or ECU an let it sit for a bit. Should loose it's memory within 15 minutes or so.

[fronton]

Does this mean the ECU has some sort of internal battery that lasts only 15 min?

[Swanny]

Might have some capacitors that need to drain out but nothing to continually "save" the data it collects

[bimmerteck]

IIRC older DME's had a cap hence the requirement to short the DISCONNECTED battery terminals.
Newer DMEs(1996+) used non-volatile memory which has to be actively cleared while the DME is powered up using a scan tool.

[fronton]

So since the DME is from '91, I do need to put the pos and neg cables together and put the ignition to position I?

[bimmerteck]

Ignition position is irrelevant in this case. Battery cables do need to be disconnected from the battery and shorted. (I typically put a jumper on them and went for a smoke break.)

[nando]

A capacitor will only hold a charge for a few microseconds - you dont need to short any cables, and you certainly dont need to disconnect it for half and hour.

5 minutes is plenty. You could just unplug the DME instead of the battery so you dont have to reset your clocks and radio presets.