Originally Posted by Lagunae92
However BMWs techs are told to do it. I've tried a few other options, including directly from the battery. Are you from the CAS unit?
That's correct. The CAS unit has a constant power source so that you do not lose any settings. This is per the instructions from bmw for the v2 wheel. The previous generation wheel tapped into the obd2 port power source. A power source no one has able to find in the M3.
In your case, the shift light settings might be reset from a power interruption. People have noticed that tapping into the cigarette power source only allows for 30 min to an hour before the settings are lost. That is with the car off though. If you are losing the settings while driving for an hour, then perhaps there might be drop in voltage somewhere.
I would make sure that your dealer connected the power wires to the CAS unit. You can check by removing the driver side panel underneath the steering wheel and looking up at the CAS unit. Two wires should be tapped into the bundle of wires connected to the unit. However, since your dealer did the install, it might be best to have them take a look and recheck their work.
But if wired correctly the settings should save every time you turn off and start the car.