Do we need radio codes for our car in case the battery dies? I did not find a code in my manual.
Also, do you have a spare battery in the trunk next to the spare tire? Mine does not have one and I see no cables for any battery to connect to.

 

I recall being able to access my radio code via MB Online.

 

Yes, that is correct - I was just in the owners area of MB USA yesterday. Once you add in the cars VIN, you can get details of the radio code.

 

I'm pretty sure you don't need a radio code unless you move the head unit from one vehicle to another. Once the radio is installed and enabled for a vehicle it verifies that it's in the right vehicle via the CAN bus and pulls the VIN from the ECU. If there is a match things go on fine. If there is not, you need to mate the radio to the new vehicle it's installed in.

I uninstalled and re-installed my head unit twice already, never needed a code.