Ouch...I am not sure I would have spliced the car side of that connector for your bypass- but it’s always reversible, I suppose.

I guess I cringe a little when I see spliced E53 wiring - which is my baggage.


That fact that you have created a bypass (which I presume works? ) from the car side of that connector tells me that the harness from that connector to the trailer plug (trailer side) is bad. I would pull your custom harness out and double check your wiring.