I have the very same problem of loosing my BMW 740i settings when I have to disconnect the Negative terminal of my BMW in order to safely replace the oil cover gasket.
My BMW manual helps me to reset the alarm and I am able to drive it. I still lost my large NAV display and my radio only plays for 2-3 minutes then it cuts off. I can still manage to view the MPG display on the odometer cluster via the control on the steering wheel, but I could not able to set the clock.
I do not have the NAV manual. Did I blow the NAV fuse or the NAV system when I connected the Negative terminal of the battery back to the car? Please help or point me to the right directions to fix my NAV display.
Many thanks in advance.