Lack of audio or cell phone functionality may be related to the failure of the audio gateway module.
Car Problem Reports
Mercedes-Benz E350 4MATIC Failed Gateway Module May Cause Lack of Audio/Cell Phone Functionality
Mercedes-Benz E350 4MATIC Problem
Average Mileage: 28,707 mi (10,123 mi - 52,000 mi)
Visitor, 2008 Mercedes-Benz E350 4MATIC, 24,000 mi
Has never worked from day 1, dealer is lost and can not fix it and charges me for inspection every time, claims this is not covered by warranty.
Just a lousy car