Hi Randy - I've attached a link below to one of our site's DIY tech articles on replacing the radio. Hopefully this will help you troubleshoot and resolve the issue you're having. If you need additional info, please feel free to post a Comment just below the article and someone will get back to you with more details. Best of luck!

Mercedes-Benz W211 Radio Navigation Display Replacement (2003-2009) E320, E500, E55 | Pelican Parts DIY Maintenance Article


-Dmitry