BMW: Transmission default, 2004 bmw 325ci, bmw 325ci

Question
I own a 2004 BMW 325ci with steptronic transmission.  There were 2 incidences when the transmission went into default mode after the engine was started during a cold morning, the first in 2004 and second 2006. The vehicle was taken in and battery was replaced. In the default mode, only the first three gears were functional. The vehicle jerked on braking and rattled on acceleration.  I called the BMW shop and was told the problem was due to low battery.  I don't think battery was the problem because the engine came on when started.  Any insight into the problem would be much appreciated.

Answer
Danny,
 I wish I could help, but this is above me for 2 reasons.  1.) It is a newer vehicle and I have no experience with it, and (2.) It's and automatic.  I've only owned one automatic vehicle, and I never messed with the Auto transmission.

 I can tell you that the battery "shouldn't" be the problem.  As you stated, the car started fine, so it has enough voltage to run the car.  It's probably a sensor of some sort.  If I could give you any advice, it would be to learn to drive a manual and never have transmission trouble again!

 Hope this helps,
 Josh