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: 75,792 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, 2006 Mercedes-Benz E350, 123,000 mi
Radio was going in and out, just shutting off coming back own for about 2 weeks and finally just went completely out...strange thing is,I had no issues until after I had my B service done at the dealer...Uhmmm
Visitor, 2011 Mercedes-Benz E350, 81,000 mi
No sound or blue tooth phone voice. Appears it is a Gateway Module problem. $800 to install new gateway.
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