Some manufacturers either put a geared up connector while in the vehicle that's a preparing around the network (Ford, Volvo) to just accept a specifically intended towing module, or have designed the trailer to get ‘detected’ via connections specifically on to the databus (VAG, BMW). With this kind of connections https://edgarlmljh.weblogco.com/4079686/the-5-second-trick-for-a-tow