Brake lights not working on trailer
 

I had my hitch installed by BMW a few weeks back on my 35d and it tows great but the problem is that my trailer brake lights don't work. Both turn signals work and the parking lights work. Also, all trailer lights strobe (like a warning) when I plug in the trailer. Any ideas?

If your trailer is running led lights you will have problems with warning lights as the system thinks there is a fault, I think because it draws less power.

Are you using the correct adapter plug?

Not sure, it's the plug the BMW provided to me.

Daus,

Did you get this working / talk to the dealer? I am having the same problem with my 35d.

Ed

Not yet, my dealer is in contact with BMWNA to figure out the issue. The only thing I know right now is that it's a computer problem. They said it's a "faulty module"

Thanks for the reply on this. I am really ticked off about having spent 65K on a car that has a jacked hitch install kit with electronics that don't work. Do let me know if they find the solution

Thanks!

Ed

You cannot use trailers that have led lights on them, that is all the problem is!

Yea, LEDS are a no go for sure, unless you add a resistor. Additionally the load (or resistance) of the trailer lights needs to match the expected load. BMW should publish this in the owners manual.

re-code vehicle

I have done exhaustive testing.. it does not matter if it is an inandecent or a LED set. Both don't work on mine.

When the dealer fitted mine a few months ago, they asked me beforehand what type of lights I had on my trailer, they said that there are different wiring looms for the hitch set up and the re-programing is slightly different as well if you have LED's

Bozz

2009 x35d with LED trailer lights fully functional. Sounds like a bad trailer light module from BMW. It happened to me on my previous x3, drove me nuts. Have the dealer replace the light module! Otherwise you'll be in a straight jacket.......

Brake lights not working on trailer
 

My 2008 X5 did not work with LED trailer lights. I took it back to the dealer just two months ago and no change. I changed out the rear lights on the trailer to regular bulbs and all is working.

I had a problem with the trailers brake lights on an E70 I installed the hitch on... The trailer had regular lights too, not LED. Ended up goint to the parts store and buying a $15 plug in trailer plug tester with LED lights to show activated circuits, and the blinkers and running lights worked, but not the brake lights with the tester as well. Tested against another E70 w/trailer, all worked right.

Final solution, I replaced the trailer module (which was only days old). All worked right since then.

turns out the dealer couldn't fix the problem. I guess they have to wait for BMW to write a software program so the trailer works with LEDs. They agreed to switch over my trailer to conventional lights and give me $600 as compensation.

Damn, they're retrofitting your trailer and paying you compensation...? That's might big of them!

there is a fix now.

http://www.bmwtis.net/tiscode/cgi-bi...0&session_id=0

anyone know the fix that's posted in the link above? it says unauthorized when I click the link.
I just installed my OEM hitch today and I'm having the trailer brake issue also. Any help is appreciated.

Did you get the car programmed? I have all LEDs on my boat trailer and there isn't any issue with the LEDs.

No I didn't get it programmed. I was under the impression that programming wasn't necessary for the lights to work. The trailer is only a small utility trailer with incandescent lights not LED. Also the turn signals work, but brake lights don't and the running lights stay on even if the lights on the x5 are off. I went over the wiring about 5x and it's definitely right. I'm just wondering if it could be the trailer light module that's faulty or maybe programming is indeed necessary.

^^ You need to get it programmed for everything to work correctly. The trailer module is installed, but the car doesn't know that. You need to add the retrofit code for the trailer module to the vehicle order.

alright I'll get it programmed asap. Thanks for the help.

I know this is an old thread, but I figured better to revive this one than start a new discussion...

I installed the OEM hitch and wiring harness on my 2010 X5d yesterday. All of the trailer lights (which are LED) work just fine, including the blinkers. The brake lights, however, do not work. Have others who experienced this determined that coding is indeed the issue? I was under the impression that the coding would get me a few PDC and rear-view camera features, but not necessary for brake light operation.

Thanks

i had hitch installed a month ago and have led tails on my boat trailer - work fine in a functions - you need the wiring coded to the car however....that is your issue - have your dealer code it....

well nice to know.
 

Guess I should be happy I have a older trailer with non-leds.

There are two different issues being conflated in the posts above.

If the lights don't work on a new hitch and electrical install, whether brake lights or turn signals, the vehicle likely needs coding. Proof is often that the rear PDC doesn't deactivate when a trailer is connected, or that the rear view camera doesn't work in trailer mode for those vehicles that support that function. The vehicle isn't recognizing that the trailer wiring module has been installed, and so it isn't functioning correctly. Think of it as a plug and play CD newly installed in an older PC, which should be recognized on boot up but isn't. The solution is to code the vehicle to specifically know that the trailer module is installed.

A second issue is with LED trailer lights. Fast flashing, or continuous flashing when parked, can be a problem with the vehicle not recognizing the low current draw of LED trailer lights. There wasn't an OE fix until BMW came out with an update (referred to above) that recognizes LED lights. The easier fix is to buy the special LED light adaptor plug (round to 4 pin flat) that includes resistors to make the LED lights draw the same current as regular lights. VW sells it, as does U-Haul. Don't know if BMW has one, but haven't seen it. Not required if you have the BMW update for LED lights, or if your LED lights draw enough current to appear as incandescent lights.

Thanks JCL - that makes sense, but I hadn't seen it described that way in the research I had done...I didn't realize coding was require just for basic operation of the trailer. I'll have it coded this week and report back

Coding did the trick - everything works just fine now. Looking forward to my first big tow this upcoming week!

Same issue
 

I am having the issue described a couple of posts above - PDC doesn't deactivate, brake lights don't work on the trailer but all of the other lights and signals do. They are LED lights, but I tried with incandescent and the same result.
I am able to do coding (or will be soon, the laptop is set up and the cable works). But when I use NCSExpert, there is no AHM module to choose from or read/write. That could I guess be the problem, but in coding - how do you actually place a module / code where none exists already? Is is factory tow-equipped, so I have no idea why I can't see that module - is it part of another of the long list that comes up?
:dunno:

Thanks, I have the same issue with no brake lights as the OP. I do need the coding done, so I guess I need to search for a friendly remote coding provider :)

[email protected] is my personal recommendation