Only in case of Volkswagen, Skoda and Seat might the coding be required.
By CAN BAP based systems (VW, Seat, Skoda – GW17V21) the Media option is disabled (most cases) therefore the car has to be coded before or after the Gateway installation. To be exact this coding is only required, if you can't choose the installed Gateway as 'Media in' in the car's menu.
The procedure is not difficult (takes 10 minutes approximately), the vehicle needs to be taken to the VW service and the “Media Player 3” option (2E) needs to be programmed by the service computer (VCDS or Autologic). After this the installed Gateway device will appear as 'Media in' in the car's menu (if the car has MDI it needs to be removed).
The supported CAN BAP head units: RCD310, RCD510, RNS310, RNS315, RNS510 (and the same but different named head units by Skoda/Seat)