secret OBC codes or unlocking the OBC is on my website, see under
Mehr Reparaturhilfen / More Repair Hin
BMW 7 serien OBC Codes
just go to my website below and then scroll down to that subject.
I use it often to check the voltage while driving, actual fuel comsumption etc.

http://tridem.han-solo.net/auto/erich/auto.htm