Seat Exeo ST PDC shutdown

Hello. I’ve been looking for help at google for days and I hope to find them here. I have a Seat Exeo ST Bj. 2012 (already with daytime running light) and have the following problem: I have retrofitted a trailer coupling with a Jaeger electric kit. Everything works without problems except for the PDC shutdown, with the electric kit is a brown/white cable that is needed as I understand for shutting down. In the instruction, however, there is nothing of where I use this attachment. It has to be measured, without PDC it should simply be cut off. So now to my question: Where do I have to connect this cable? I think in the PDC control unit but where can I find this and on which pin do I have to connect this? The service technician from Seat could not help me any more. I hope you can help me (I’m already beginning to despair) and already thanks for your efforts