Originally Posted by Tomdownunder

I'd be happy with the how to. I made up an isolating adapter for my E39 using low impedance relays to stop the check bulbs error. The E39 (1997) didn't have the trailer module like the E53 has.

The other possibility is if the US adapter is a one piece unit with wires going to the plug and socket at each end, then it would be possible to chop the ends off and just run leads out of each end, seal off with epoxy and use it as the trailer lead itself. (I have a socket on my trailer already and just use a lead which runs between the car and the trailer which can be unplugged both ends.) If on the other hand it is circuit tracks going to the spade connectors it might be a bit harder.

If you are happy to purchase one and disect it that would be great. At least that way I would know whether I can adapt a US version or copy the guts of it and make my own.