Hello, I'm Chris. Thanks for visiting Just Answer.
Is this a factory setup or aftermarket?
Factory setup on 2011 E350
I am not having any luck finding a procedure to set your car up to work this way. Would you like me to opt out and let others try and figure this out.
Does that mean that is standard for the radio to come on when you put the car in reverse? This doesnt surprise you?
I suppose it would good to let others try to answer.
Opting out now, best of luck.
If the radio is not turned on, it should only come on momentarily while the camera is active, and shut off again when the camera is no longer active. If it doesn't, then you have a radio issue and it may need to be replaced.
I'd try resetting it first by disconnecting the battery and touching the cables together to discharge any stored electrical capacitors in the modules.