Warranty took care of the aux battery and I noticed the distronic plus system seem more "active" when turned on. It was able to sense the lane markers better and make faster lane corrections. Unfortunately, the eco autostop also works all the time now...

Where is this battery located on the 2011 E63? I also have this message and brake hold doesn't work.

behind the cover on the driver side of the dash board.

Thanks for the reply. I am not sure what you mean by... behind the cover. Does anyone have a photo or diagram?

Is this the proper location for a 2011 E63? Looks simple enough to replace.

Other than the brake hold function, what else does this auxiliary battery malfunction affect?

auto start stop, some distronic features

I just read through the owner's manual and this is what it says about the display message;

"The auxiliary battery for the automatic transmission is no longer being charged. Visit a qualified specialist workshop."

Is replacing the battery the fix, or could there be more to the error message?

Distronic

The infotainment system seems to default to off when I started the car. Had my aux battery replaced today.

Replaced mine today and the Brake Hold feature is back. It was explained to me that the auxiliary battery's main purpose is to keep power to the electronic shifter in case the main batter dies. This way the shifter can be placed in neutral for towing.

That's why the owner's manual says ""The auxiliary battery for the automatic transmission is no longer being charged."

Thanks everyone for the help.