Thanks for the info! There's a 7-to-4-pin adapter in the glovebox so I hope that's all I need.

I'm still looking for a cheap wiring solution for trailer braking
 

Can you show the adapter, part number, and manufacturer? Perhaps it'll be a cheaper solution than buying the (factory) AHM trailer module & wiring harness, or even the work-arounds I found that might possibly work for me.I've been procrastinating about getting my X5 ready to use the electric trailer brakes on my 2225 lb trailer for over two years, since I last posted on this thread.

I still haven't pulled either of my trailers with the X yet (no need to use the non-braked utility trailer, nor have I used the braked squareback for camping in the past year...I used my '04 Chevy 2500HD just once, in April 2022, since I hadn't gotten a 7way for the X5).

If there's a place to plug in the 7-pin/4-pin adapter, then the previous owner already installed some way to wire up a trailer. (Whether that was OEM or hotwired, I can't say.)



But a 7-pin to 4-pin adapter certainly won't do the job unless there's a place to plug it in. And to get a place to plug it in, you have to either have the OEM towing module or hotwire it onto the brake lights.



Workingonit, if you don't have a brake controller then you can't use the electric brakes in your trailer no matter what. Even if you have a 7-pin connector from an OEM towing module in your X, there's nothing powering the wire that activates the brakes unless you put a brake controller in.

just trying to decide exactly how to configure my future 7-way
 

I already have a 4-way installed by the previous owner though I haven't even plugged my trailers into it, he used it before we traded to haul his motorcycle to races, (on the utility trailer that was also a part of the vehicle trade...i.e. Chevelle for X5, car hauler for utility trailer). I assume it worked OK.
Attachment 83851
Attachment 83852

Since I don't know whether the 4-way was wired up in a way (by the PO, an electrical engineer, who should've done a better job of it!) that would not upset the finicky BMW light module (as I've read that it might), I don't know exactly what adapter(s) I might need for a properly operational 7-way install. I don't have any idea what the three relays he wired in (in a photo above): perhaps to modulate flickering lights, or lights registering as a fault with the LM? I don't know, since he seems to have dropped off the face of the planet during the past year, so I can't ask him. If I do need to get a factory harness and AHM module, then at least I have the requisite connectors in my trunk to hook up to them (again, I'm not sure of which one to use, as there are four back there.
Attachment 83853

No, I haven't yet installed a brake controller, as it would be a premature expense prior to determining the correct wiring needed to make it work smoothly with the X5. I've installed many controllers before, so I see no problem ahead.

He just spliced into the brake light wires, you can see the splices in your picture. You will probably have the dash light up when you plug in. Not sure exactly though, the relay coils may draw so little voltage that it won't trigger the LCM light alarms.

I'll have to hook it up soon, as I'm planning a camping trip this spring (X5 for excursions under 200 miles round-trip, or the 2500HD for longer trips...depending on my camping group's choice for the spring gathering). I suppose that, if I can't go 7-way in time, then, with the trailer only weighing 2225 lbs and the 3.0i tow-rated for 5000 lbs, I could use the 4-way anyhow (minding traffic a little closer than usual). We'll see.

I sorta figured that the three relays might have something to do with preventing the LCM module from acting up. I won't know until I actually test it, first.

You just need to plug it in to the trailer and tap the brake pedal. The alarm will be generated immediately if it is going to trip.



I agree, if the total weight of the trailer is only 2200 lbs, you might be fine without a brake controller. A few times I've forgotten to put the brake controller back in (since I take it out of the car during the winter when I'm not towing) and had to stop abruptly with my trailer (which is about 4,000 lbs loaded) and it stopped pretty fine. A bit slower, but not dangerous by any means. The E53 has really good brakes, even the 3.0.

The factory module does more than stop lamp warnings (and allow correct monitoring of the trailer lamps) - when it detects a trailer is connected it also disables the rear PDC and alters the ABS braking programme to take the trailer into account during heavy braking.