Lack of audio or cell phone functionality may be related to the failure of the audio gateway module.Google+
Car Problem Reports
Mercedes-Benz E550 Failed Gateway Module May Cause Lack of Audio/Cell Phone Functionality
Mercedes-Benz E550 Problem
Average Mileage: 8,750 mi (7,500 mi - 10,000 mi)
Visitor, 2010 Mercedes-Benz E550, 10,000 mi
The screen for the audio electronics says DEVICE UNAVAILABLE, and none of the audio electronics will work. This can happen at anytime, when you are just starting up or driving down the road. I have recorded this on my cellphone and showed it to the Mercedes service department and they simply said they could not duplicate the issue.
intermittent audio failure; dealer claims it needs MB input to figure out cause and enable warranty repair