Long time lurker, first post...I just installed the Curt hitch #13136 on my 2014 Q5 and found that the wiring was a bit more challenging. Following Bob Green's post and using a Tow Ready #119190 Module by Tekonsha, I offer some things to note for others doing the same after hours of trial and error.

1. The Scotchlock connectors do not work well on the Audi wiring as the wiring gauge is too small to always make a good connection and they can cut the wire resulting in no connection at all. I ended up using crimp on butt connectors.

2. On my car, the wire needed for the left turn signal (located in the top orange plug) was gray with a red tracer, not gray with a black tracer.

3. The bottom black plug contains two solid gray wires so you have a 50/50 shot of getting the correct one. On my car, the correct gray wire was in the corner of the connector.

I hope this info helps.

 

This is a great post, worked just like it should. I did learn one more thing that I didn't see posted. The electrical connector that connects the rear deck latch to the wiring system, behind the chrome trim panel on my 2012 Q5, must be connected for the system to sense that the rear deck lid is closed. Otherwise it operates as if it is open and the bumper lights work, not the deck lid lights and hence the trailer lights don't work. If you took the trim piece off to access the rubber grommet for the wires be sure to reinstall it before you check your work. Thanks for figuring this all out WAY cheaper than the dealer and WAY better than the etrailer method of installing it in the hatch door.

 

A few points to add to Bill B's post;
just finished installing a Curt C59236 in my wifes 2011 Q5. Thank goodness for khaven's original post showing the actual pin#s. re; there are two gray/black wires to T17P and of course I had originally spliced into the wrong one. hair pulling event #1. Then once i figured that one out I was testing the heck out of the 4-pole trailer plug and -- nothing. finally reading this ENTIRE THREAD to the bottom i see BillB's post that you gotta have the deck lid CLOSED in order for the lid lights to work. hair pulling situation #2. *whew* got-er-done though. thanks for the posts everyone.