Trailer wiring module question

[David D]

I just installed a factory hitch kit on my 2005 4.4i. The install went very well thanks to several contributors to this forum! I do have a question about the trailer wiring module. If I connect a trailer and the module isn't recognized, will the trailer lights function? I will gladly take it to the dealer if necessary, but obviously, don't want to spend dealer $$$ if it's not necessary.

Next weekend, we are taking a U-Haul trailer to get our daughter from college for the Summer and need to know if I will need to have the system updated or not BEFORE we pick up the trailer. What's the worst case scenario if we hook up the trailer and my X5 doesn't know it's there?


David

[Roadkill]

you will need to have the module coded before the car will recognize the upgrade.

[X5Ghost]

Well before you spend the money at the stealer, hook up a trailer and make sure all lights work as well as PDC when backing up. If not, the you need to code it!
For some reason some do and some don't! I think the cutoff is somewhere in 2004 production but not sure when?

[David D]

Yeah, I've read that nothing needs to be "coded" per se, but that the system needs to just recognize that the module is there. Worst case, I can buy and rig up some trailer lights and test it. If the lights will function correctly with or without coding, I won't panic if I get to U-Haul Friday and at least the lights work. I'm just trying to find out what happens if my X5 doesn't see the trailer module in case I can't get to the dealer in time.

[JCL]

Just go to a local Uhaul, tell them you are renting next weekend and just want to check the wiring. You don't have to take a trailer out.

[David D]

Good suggestion, and I will give that a shot.

However, I guess I haven't phrased my actual question well enough though... I'd really like to know what happens if you connect a trailer and the trailer wiring module isn't recognized? Do the lights still work? Do you have to manually shut off the PDC? Do you get a lighting fault code? Inquiring minds (at least this one) want to know!

David

[williak7]

Originally Posted by David D

Good suggestion, and I will give that a shot.

However, I guess I haven't phrased my actual question well enough though... I'd really like to know what happens if you connect a trailer and the trailer wiring module isn't recognized? Do the lights still work? Do you have to manually shut off the PDC? Do you get a lighting fault code? Inquiring minds (at least this one) want to know!

David

My assumption is they would not work if it was not coded. I installed the hitch, but didn't have time to install the module. When I connected the trailer lights they of course did not work. I connected the module sometime later and they worked. I have a 2005 4.4 and did not have to get the dealer to code it.

So my thought on this is if it is coded correctly they will work and the PDC will disable once you connect the trailer - stops the beeping to signal something is behind the vehicle.

I hope this helps.

Kevin

[David D]

Thank you Kevin. That's what I was looking for. I'm going to Uhaul today and give it a try. With any luck, the lights will work, indicating that I don't need a trip ($$$) to the dealer.

[David D]

Ok, just left Uhaul and the lights work. Did not actually hitch the trailer, but plugged in the lights and they all checked out. Put car in reverse and the PDC activated. I don't know if that's normal, but was able to deactivate the PDC with the button.

[JCL]

There have been different reports of the results of not doing coding if it is in fact required.

The module may not be properly recognized, in which case the lights may work partially or fully, but the rear PDC does not turn off (you can always just do that manually).

There may be problems with the LED lights on the trailer if it has those, resulting in a fast blinking and intermittent flashing when the lights should not be on, as the module tests the circuit. This is all different than if there is not a proper ground, and the lights blink too fast as if a bulb is burnt out; this is solved by using a proper ground. BMW did have a software upgrade for some specific models to address the LED problem, or you could use the LED adaptor that U Haul and others sell for Volkswagens and other vehicles (we all have the same electronics, made by Bosch).

It may all work just fine.

Some have suggested that coding is required to get the trailer stability mode to work in the DSC. I don't buy that, as the module doesn't include that coding, it is built into DSC. I have installed modules that said no coding was required for those specific vehicles and where the TSC was included in the features. I have always figured that if all the obvious things worked (all lights, plus PDC cancel in the rear) then the vehicle knows there is a trailer, and TSC will work if you put yourself in a situation that the sensors determine it is necessary (like DSC intervention when corning too fast, it indicates on the dash and intervenes). I have never had a trailer swaying so out of control that TSC has intervened on me, and I don't think it is actively intervening without some type of dash indication.