A 2021 updated Trailer hitch & brake controller thread
 

So by now if you've made it into this phase of e53 ownership (owning a 15-21 year old SAV) then towing may be just for you, but the cost of a genuine BMW system is prohibitive at $1,200+ dollars for almost the same thing you can get for much less, and on these vehicles the cost could easily be twice as much with labor installed as the cost of the entire SAV! Considering my dd X5 is a 216k mile, 2001 3.0 AT, its definitely the case with my tow mule! But I have maintained her well so she is definitely up to the task.

Reality check #1. Using a Curt hitch (cost: around $100 shipped) rated at 5k/6,000 lbs (depending on engine size) can work as it uses heavy duty square tube steel and has beefy welds throughout, but the hitch has a couple caveats:
1) The riv-nut that attaches the longitudinal stabilizer bar and rear subframe is difficult to mount properly without tack welding it in 3 spot to keep it from spinning while tightening it up so it expands/sets properly.

2) Scuff and coat the entire hitch with epoxy bedliner spray twice, which keeps it rust free for a long time overall. From the factory, it is shipped without a package and gets some coating removed around the edges. Its a standard coating which is weak rust control by BMW standards. $5 worth of Bedliner solves this issue.

Reality Check #2
Brake Controller is pretty straightforward, but with one important issue yet to be solved:
1) Clean brake pedal trigger wire: that needs to posted freely on the web and it should be on a sticker and the wire itself- which should located inside the spare tire area and also where the tail light wiring is, to avoid serious injury or death: The exact location and color of wire to signal the brake controller to brake CLEANLY, and the color codes for the 4 flat adaptor installation (brake, turn, tail).
2) I used what was available, which was a brake light wire which due to its BMW bulb checking circuit, makes the trailer brake controller go crazy- sporadic braking on its own, eventually controller calls a short circuit message, and then no brakes on trailer! It was so unruly it caused the vehicle to go into limp mode twice!

3) Right now, the Hopkins brand Impulse model works perfectly without the headlights on, so I guess its not checking or throwing random testing voltage thru the circuit while the tail light markers are not lit. It's soft upscaling of brakes keeps the braking from being jerky, but there is a small release jerk upon releasing the brake pedal.
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4) in conclusion, BMW and these brake controller manufacturers should have this type of thing standardized for the consumer since American consumers have been towing tons of trailers for 60+ years, and buying a trailer of sorts on a whim and safely towing it home in a matter of hours is has been considered 'the norm' for most Americans, so it should be an embarrassment and their legal fault to these manufacturers to not have the ability to readily identify the necessary wiring and safely install a brake controller without a degree in electric engineering.
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:beerchug:

I would like to complete this thread and make it a DIY article for e53 owners, any input would be appreciated!

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.

also trying to piece together a tow package substitute
 

I recently traded my old drag-racing '66 Chevelle (+ dovetail trailer w/all-wheel brakes) for a '01 X5 3.0i (+ 4.5x12 single axle utility trailer, no brakes); the previous owner had installed a used Drawtite X5 hitch, plus the rudimentary 4-pin plug in order to tow the trailer with, at my request. There is no brake controller or tow package installed.
Attachment 80978Attachment 80979

He just ran the wires to the taillights/brakelights (surprised he did it using red-neck engineering, since he is a degreed EE), and not thru the LCM. I found this statement somewhere, somehow on a BMW forum??: That quote made me wonder if I could piece together the components needed (cheaply) in order to make the X5 ready to tow my braked 2225 lb home-built squareback trailer.
Attachment 80980

Perusing etrailer.com, I found that they say I just need an electric brake controller, a 4-pin to 7-pin adapter, and their universal installation kit; but on ebay I found a kit that uses an additional "circuit-protected" 4-pin wiring harness. Somehow, I suspect that BMW has something hidden that will not like the add-on aftermarket wiring (assuming I get the correct combination of parts). $260, plus $120 for the circuit protector wiring. It was much easier on the plug & play wiring-up my (old model) Hopkins Impulse brake controller on my '04 Chevy 2500HD.Attachment 80977

The "brake signal wire" should be pulled from the HMCSL wire at the LCM in the passenger footwell. I dont recall the color.

If you get a aftermarket light control module, you need to get one that is PWM compatible, I used a reese one on mine.

The brake control you are talking about, hopkins impulse is a timed brake controller, meaning when you step on the brake, it activates the trailer brakes for a period of time, I would never use those types of controllers, I have seen too many of them fail or burn up the trailer brakes. It is best to use a proportional control, they are more expensive, but they work better.

I used to do hitch and wiring on vehicles and RV's I have installed hundreds of systems, make sure you put circuit breakers were applicable and use the proper gauged wire.

As far as the hitch itself is concerned, when I was looking for mine about 6-8 years ago, there were only 2 types, the type that installs like the factory hitch at the bumper mounts, and the type that has the bar that runs under the car past the spare tire. I dont like the look of the bar running under the car so I opted for the OEM type. Looking now I cannot seem to find the style I got. One of the things that the factory hitch does, it replaces the bumper mounts with hardend, and Longer ones, which you cannot get with the aftermarket ones. So I fabricated my own, as well as installed steel plates where needed to stiffen up the body. I used the highest grade bolts, and put lock tight on everything. I went this way because as you have found out, finding an OEM hitch has become impossible, and when you do they want a fortune

sounds like a better plan
 

I was writing my previous post when you posted this answer. Sounds more reliable than piecing together non-BMW parts, and hoping for good results, As-is, I'm not having any error messages (save for the passenger airbag), and don't wish to trigger any new ones.

The hopkins Impulse is not activated for a period of time, as that is only a misunderstanding of its name.

When setting it up, you can choose 99 intensity levels for braking, and once set it remembers that. When you activate the brakes, it takes 3 seconds to go from 1 and steps up to the maximum preset intensity, so for shorter corrections in traffic slowing, you don't need full braking but if you need to come full stop from 75, it will hold the max power after 3 seconds indefinitely. In theory it sounds just okay, but in reality it works just fine and has some advantages over proportional braking, such as if your tow vehicle had braking power fade, or suddenly has partial/full brake failure, proportional isn't going to know to stop harder to compensate for it.

I made a wiring harness out of a brake controller wiring kit and a couple extra wires as well, then spirally wrapped the bundle with that fuzzy harness tape just like BMW does, it took about 20 minutes. I grabbed all the necessary electrics from the spare tire area and utilized the factory fuse block. Ground went to the trailer hitch frame itself. That may be where some improvement could be made, and run a short ground wire off the controller, to decrease feedback issues.

Thanks for the replies, but to repeat- Does anyone know where and which wire gives a clean brake pedal signal for hard wired controllers? Mine is pretty much done and towing/braking fine in daytime.

Thanks Again!

That's similar to the route I went, but I already had 4-way wiring, so I picked up a 4 to 7 way adaptor receptacle with bracket and it also has the 4 way still available next to it too, mounted just left of the 2" Receiver inside the oval knockout.

Both of aftermarket e53 hitches came with steel stiffener plates for the bumper mount area that are welded to the hitch structure.

I probably wouldn't recommend this job to someone who doesn't have the technical and engineering skills either. But that being said, I do have the skills. Degreed in Aircraft engineering and mechanics (including electrical), applied science, physics, 4 years in Automobile related repairs education, and 32 years in experience.

X5's are coming into junkyards and pick and pulls at a steady clip these days. If you are quick, you might find one with a factory hitch and harness.