CD changers, command units, voice control units, PSE units, and Tele Aid units are prone to failure, especially in early models.
Car Problem Reports
Mercedes-Benz CL55 AMG CD Changers and Command/Voice Control/PSE/Tele Aid Units May Fail
Mercedes-Benz CL55 AMG Problem
Visitor, 2003 Mercedes-Benz CL55 AMG, 89,000 mi
cd changer will not eject cartridge and audio doesn't work at all on the left side of the car.