Originally Posted by Bdc101

The reason that BMW didn't have the brake module figured out is because this was their first SUV and was also one of the very first "crossover" SUVs. I don't think anybody making unibody vehicles of any kind had towing very well figured out at that time (1999).

I have one more thing which I can universally recommend: buy a reproduction wiring harness from this ebay seller (https://www.ebay.com/usr/bahgelsson who is a member here) along with a used towing module. It is easier to get this working than it is to wire up an aftermarket wiring for a towing harness (i.e. no coding required, it is plug-and-play at least for pre-facelift cars). It is also very easy to add a brake controller using the factory setup.

(The harness has been OOP for several years and this is the first reproduction one available. I towed for several years with aftermarket wiring and just got used to the errors on the dash. I can heartily recommend doing it the "right way" with this equipment.)


I don't even have a degree in electrical engineering! I'm just a simple-minded mechanical engineer.