Lack of audio or cell phone functionality may be related to the failure of the audio gateway module.Google+
Car Problem Reports
Mercedes-Benz E350 Failed Gateway Module May Cause Lack of Audio/Cell Phone Functionality
Mercedes-Benz E350 Problem
Average Mileage: 69,240 mi (25,000 mi - 133,000 mi)
Visitor, 2011 Mercedes-Benz E350, 25,000 mi
No audio/phone/navy off and on...
Visitor, 2007 Mercedes-Benz E350, 133,000 mi
Audio gateway never sleeps and drains battery. Gateway now completely failed and dealership wants $2,295.00 (not inducing labor) to fix it.
Visitor, 2009 Mercedes-Benz E350, 90,000 mi
No audio. Only an odd "tick" "Tick" "Tick tick" sound alternating from each speaker. Command unit displays fine, satnav, radio, etc, but no sound at all other than that described above.
Visitor, 2011 Mercedes-Benz E350, 73,427 mi
No sound, radio, CD, phone. Everything else works fine, Navigation, system settings... etc.,
Visitor, 2006 Mercedes-Benz E350, 49,000 mi
No audio, no nav display, no cell phone funtion