All Gateway devices emulate the CD changer (CDC) function (or MDI function), this is how the car can recognise them. There are quite a lot of car types which support an external CD changer, but not all of them are supported by the Gateways. The key for checking the compatibility is the head unit (radio or navigation type) of the car.
We have a database of the officially supported car head units, we also tell there if there are also some exact compatibility points you need to check in case of your car individually. Therefore using this Compatibility selector is highly recommended, you can find it on the left side of the official Dension webpage:
If your car head unit is not mentioned in this database, then it is officially not supported and most probably the Gateway can't work with it. But even if this is the case, but you already have the Gateway device, then you can try if the Gateway will be recognised as a CD changer (or Media In). For further help you can still check all the Knowledge base sections, first of all section N.