This is not a difficult install, once you know what to do. That's the rub, and also the reason for this post - to save others from the hours of confusion and research that I went through.

Note that this covers only the 4-wire setup without brake control. If you need a 7 wire or other system you are OYO, although the taillight information below should still be useful. Since Audi uses a PWM lighting system for its LED lights, you need a compatible controller.

I purchased a Curt 56200 PWM control module, even though Curt had not tested it on the 2011 Q5 and could not say whether or not it would work. The Audi parts person told me the 2010 and 2011 Audi OEM trailer wiring modules were the same, and that gave the confidence to take a chance on the Curt, which they do list as OK for the 2010 Q5. I also bought the Curt battery wiring kit, which has an in-line fuse to protect this new circuit.

Fortunately I know an Audi service tech, and he pointed me in the right direction and give me half a ream of wiring printouts. I'm not sure I would have attempted this without his help!

To cut to the chase, the wires that you need access to all plug into the "Comfort System Central Control module", which is conveniently located behind the pop-out panel on the right side of the tailgate area. It's the unit on the upper right in the picture below. I had clip leads connected to make sure everything worked before making permanent connections. The red connector on the right was a handy source for +12 volt power.



I stuffed the Curt module into an empty slot in the fuse area, where it sits pretty happily. I connected the white ground wire to a ground stud on the rear wall of the compartment.

At one point I almost gave up on this whole project, until I figured out that the tailgate (and hence the taillight) wiring is rerouted when the tailgate is open, which explained why I couldn't get anything to work when I was sitting there testing everything with the tailgate open! Once I figured that out, the rest of the project was a relative breeze. So, here you go:

In the picture below, you will see two rectangular connectors. The upper connector is T17p and the lower connector is T17o. You will need to make the following connections to the Curt module:

Curt RED brake/tail light --- Audi T17p pin#11 gray/black

Curt YELLOW left turn --- Audi T17o pin#12 black/blue

Curt GREEN right turn --- Audi T17p pin#13 black/green

You can't see the wires from the picture below, but this gives you a rough idea of what you're doing:



I cut a slit in the upper of the two rubber plugs in the lower rear body, and ran the 4-wire harness through the slit and out under the lower fascia to the hitch area. This is all very accessible and makes for easy routing.

Now all that's left is the battery connection. I found an extra stud on the battery that was upstream of any fuses and connected the fuse holder to it. I ran my battery wire to the Curt module along the same path as the red battery wires. Here's a view:



And a view of the completed installation:



- Ken H.

 

Nevermind, figured it out, I had the wrong controller, great DIY!

 

so, what do you do with the brown trailer light lead?
rt works, lt works, brake works, running lights work without the brake depressed. press the brake and the running light output doesn't work. what am I MISSING?

 

zsquare,

I had the same issue but I was trying to re-use a controller I had for my 2008 VW Touareg. I did not have the Curt 56200 PWM control module. When I bought the 56200 and installed the power kit it all worked right. The stop and tail lights actually run together on my 2009 Q5. It sends one signal for the "lights" and another for "stop" but they are on the same wire. If you get the Curt 56200 PWM control module and hook it up as per the above you will work perfectly. I just finished this, this weekend. One thing I would say to Curt, those T-Taps were horrible. The wires are so thin on the Audi I had a lot of problems where the t-taps didnt cut through the insulation so I had to solder the wire connections.

Good luck!

 

Hooked up to the trailer and like magic everything worked fine. So confused. Oh well it's done.

 

This is great!

 

Thank you for posting this!
Do I understand that with the 56200 module you had no requirement for VCDS coding for the trailer/hitch?
I take it you are stuck with the reverse sensors continuously beeping since this setup is unlikely to disable them?
Any caveat to this setup as opposed to the OEM install? I got quoted 1800$ by the stealership to get this done and there is no way in hell I am going to pay that kind of cash for a hitch.

Would really appreciate confirming the above!

Thanks in advance,
Mat

 

Mat - you are correct, no coding was done. And yes, you need to disable the rear bumper sensors each time you shift into reverse with a trailer. A minor annoyance. I'm with you on refusing to pay $1.8k for a hitch install.

- Ken

 

How do you go at disabling the rear bumper sensors? I dont seem to have that option on the onboard computer. Do you have to VCDS them out ?

Thanks again for the great help!
Mat

 

Has anyone had problems post installation? I connected my Curt module as described above and it worked fine. After about a week the break lights stopped working on the trailer. I tested the connector at the hitch and as suspected there was no power getting to the brakes. I replaced the Curt module and all was well again. This time after a week the tail lights stopped working. Any advice?

Thanks,

R.