That was the 'traditional' way of doing things. Now I believe the magic Trailer Control Module detects current flowing (or not) and advertises the fact over the CANBUS. So that the little trailer dash indicator illuminates and the reversing module is disabled along with the rear fog lights.
Towbar electrics used to work fine (2 years ago) but on testing with two different trailer setups today .. nothing.
Went right back to the Trailer Control Unit (the box behind the trim) that takes CANBUS in and then drives the appropriate conenctions down to the trailer socket.
Question: Does...