I want to highlight my experience installing a CURT hitch on my 2005 Porsche Cayenne and the Porsche wiring harness and control unit. I bought a Pace trailer and wanted the lights to work, so I installed the Porsche OEM wiring harness and new control unit.
You will need these parts:
1) Porsche Part 955-618-040-10 Control Unit
2) Porsche 955-612-506-00 Wiring Harness
3) PNA-955-118-93 trailer hitch Connector (this is the 7 pin Pollak connector) This is where the factor wiring harness plugs into at the center of the bumper hitch location so you can plug in a trailer harness. This is just a socket connector, weatherproof with a cover)
4) PNA 955-127-08 7-4 way Adapter (this just converts the 7 way adaptor to a 4 pin adapter)
PNA-955-118-93 is the same thing as Pollak 11-893P 7 way sealed RV OEM Socket that you can buy on amazon.com for 11.60
Also will need Pollak Mounting Bracket for Pollak 7-pole Rv Style Trailer PK12711U
5) PK12711U Mounting Bracket for Pollak 7-Pole, RV-Style Trailer Connector - Vehicle End
6) 18140 No-Drill Mount Bracket, Short (to install the socket bracket to the curt hitch without drilling)
First, you should have the proper tools to take off plastic trim pieces without breaking anything. You should have patience and have experience working with cars, otherwise this can turn out to be a very difficult project. Not for a novice.
To remove the bumper you have to take off the taillights since there is a screw located there. Then there are screws found in the wheel well and under the bumper. There is one screw in the wheel well that is hidden from sight and you have to bend the plastic trim piece to get access to it. After removing the bumper you will see the location of large bolts on each side of the metal bumper that you will remove and then install the Curt hitch. The Curt directions are good so use that has a guide.
As for installing the Porsche wiring harness this is what I noted. The wiring harness itself is simple to install since the connectors just snap in. One connector is colored green and this matched the green socket that it plugs into and the other black connector goes into the new control unit. There is already a purple connector prewired in the cayenne that plugs into this control unit. Once you have these plugged, everything will work when a trailer is connected to the car and only if a trailer is connected to the car. The control unit can sense if something is connected.
Getting the wiring harness and control unit installed was a little harder. If you don't have a CD changer installed you should be able to use remove the little trim piece in the truck on the passenger side , it just comes off, and reach in there and install the new control unit and plug the new wiring harness into this. You can see the prewired purple connector sitting there wrapped in grey foam and it's located right where the control unit will be installed. However if you have a CD changer you will need to open up trim pieces and this is the hard part.
One way to do this is to take out the carpeting in the trunk floor, you will see screws for the tie down clips and 1-2 other screws. Then you will see screws for the sidewall carpeting. Then take off the top center light located on the ceiling, and pop off the top passenger side trim using plastic trim removal tools. Be very carefull because if you use too much force you will break the plastic clips on the trim pieces. There is also a screw on the side wall coat hanger. After popping off the side trim piece near the window (d pillar) you can bend the side carpet trim piece in the trunk outward so you can get you hands in the location of the new control unit mount. There is a piece of black vertical plastic that the new control unit just gets attached to with 1 screw. Very easy and the location of this is exactly where the purple connector is, which is wrapped in grey foam.
You will also need these two parts to install the 7 pin socket to the back of the car. The PK12711U mounting bracket is a metal bracket that perfectly fits the pollak socket and since it's very hard to drill into the metal of the Curt trailer hitch you are better off getting part 18140 which makes the install very quick. If you have all these parts then the installation will go very smoothly.
PK12711U Mounting Bracket for Pollak 7-Pole, RV-Style Trailer Connector - Vehicle End
18140 No-Drill Mount Bracket, Short
I got both from a website called etrailer.
I could have installed the control unit without removing the carpeting and trim pieces, but I didn't know better. The location of the new control unit mount and the purple connector were visible and I could reach it with my hands.
Using the factory wiring harness and new control unit work great. There is no need to program anything using a Porsche computer. Everything was plug and play.
The time I spent doing this was not worth it. It would have been better to get the parts on my own and just give it to a dealer to install or have an aftermarket porsche guy install it.
Unless you like to work on your car and don't care about how long it takes, it's worth it to pay someone to do it.