How do you make the radio work when removing the navigation drive.
The control buttons and switches on the function keypad in the radio control panel and navigation unit are read in over the micro controller I/O ports and transferred to the central processor. Depending on the system function, the button actuation is processed in the central computer or transmitted to the other system components via the Media Oriented System Transport (MOST), the Controller Area Network bus class B (interior) (CAN-B) or the Controller Area Network bus class C (engine compartment) (CAN-C) in the form of a data telegram.
If the ON/OFF button on the rotary switch is pressed, the radio control panel and navigation unit switches on. The volume is regulated at the rotary switch for the audio source adjusted in each case. The function keys switch over to the audio source desired by the user.
This information is supplied by the Alldata Automotive Information website.
This is a small description of the Navigation/Radio system. As you can see it is very complicated and all of their communications with each other and the rest of the car are tied together. When you remove part of the system the other won't work until the missing unit is replaced and reprogrammed for its proper operation.
If you had the unit removed for repair then you are stuck with out a radio until the repaired unit is replaced. Sorry.