Part 1 of 2
I know I am not the first person to tackle this project but I wanted to share my experiences with the group while it is still fresh in my mind. Hopefully my summary will help out the next guy. If you are going to tackle this project I recommend you locate on the web a copy of the Porsche AFTERSALES installation guide for the tow system. Unfortunately, I do not know how to attach it here.
I custom ordered my (US Spec) 2005 Cayenne V6 in November of 2004 and took delivery of it in February 2005. Like an idiot I did not have the factory install the tow system. At the time the option was about $1000.
In 2011 my body guy installed an aftermarket CURT tow hitch for free! The cost of the hitch was $180, ordered directly from CURT via their website. I am not by any means a towing expert, but my impression of the CURT tow hitch was very favorable. It seemed to be well built, beefy and had a nice powder coat finish. I am aware of three main differences between the CURT tow hitch and the OEM product.
1) The safety loops used to connect a chain from the trailer to the hitch run perpendicular on the CURT hitch and are parallel to the receiver on the OEM product.
2) The CURT hitch does not have provisions to connect the bracket of the 7 blade Pollack electrical connection to the hitch. Currently my Pollack connection is zip tied to the safety loop until I can work out a solution for the metal Pollack bracket.
3) The OEM tow hitch is rated at 7,700 lbs. towing capacity, and 660 lbs. tongue weight. vs. the CURT unit at 6,000 lbs. & 600 lbs.
The CURT hitch does not have accommodations for the tow eye on the hitch. However, I suspect if I ever needed to flat bed the SUV it would make more sense to utilize the tow hitch than a tow eye.
Below are photos of the installed CURT tow hitch. I came across quite a few write-ups on how to install both aftermarket and OEM tow hitches. My CURT tow hitch required a little bit of trimming of the bumper cover, but if done properly, not even noticeable. In fact, you need to be underneath the car to see the cut.
My tow hitch worked well to secure a bike rack on the rear of the SUV, however I found a need to begin towing a small trailer. Therefore, I needed to get the appropriate electrical connections for trailer lights. There are several ways to accomplish this, obviously the OEM surge brake system and an aftermarket solution.
Some of the contributors on other forums state that for towing small trailers without brakes, there is no need for the factory OEM surge brakes, and splicing into the existing tail lights is sufficient. Again I do not have any experience with this method and cannot attest either way how well it works. My concern doing it this way is that it may trigger a warning on the dash.
Others on the web report using aftermarket products. A couple that come to mind are Prodigy and the Curt brake controllers, but a search of the web would reveal even more. Again I do not have any experience with these products.
People who had the OEM surge brake controller commented how well they towed large trailers and liked the fact the tow controller module interfaces with the dash. In the event a trailer light burns out there will be an indication on the dash, and when you use the turn signals there will also be an additional blinker on the dash.
I decided to go with the Factory tow module route . . . Our host sells all the necessary hardware. The factory AFTERSALES installation documentation lists all the major hardware and accessories needed to properly install the hitch and electronics. Below are the major components
1) 955-618-040-10 Control Unit -$218 from our host
2) 955-612-506-00 Wiring Harness -$236 from our host
3) PNA-955-118-93 trailer hitch connector -$18 from our host
My research revealed that there are also another part numbers for this project. The Touareg uses the same system as the Cayenne. Since the information was so sketchy on how to do this project, I was worried I would buy hundreds of dollars of new hardware just to have them collect dust in my garage. I was able to pick up a “new” Westfalia tow module controller and wiring harness for $260 delivered which the seller claimed he bought new but never installed for a 2004 Cayenne V8. In hindsight, worked well for me, however, if I had to do it again I would have bought the hardware new because there wasn’t much difference between buying the Westfalia parts from a third party than buying new from Pelican. ALSO, here is an important point, my research showed that there are several used tow module computers available on Ebay, but if you go that route be careful what you buy. There are several early versions of the tow module available. Some forum contributors stated that early versions needed to be reprogrammed/reflashed at the dealer. I wanted to avoid a trip to the dealer at any cost. The Westfalia part number for the tow controller is
7L0 907 383 (Version designated by a Letter)
The part I bought was 7L0 907 383 F. This is an uncommon tow module controller because it has the ability to control the retractable tow hitch. Most tow module controllers have two connection blocks, the F version (or versions that control the retractable tow hitch) have a third connection block. In my install I did not use the third block and the controller still worked fine, (no errors on the dash or on the Durametric Scanner).
The wiring harness was also a Westfalia product, part number
327 007 321 003
Though this part was advertised as new, one of the pigtails had two of the connection tabs broken. However, fortunately for me the pigtail still plugged snugly into the appropriate connection block AND it was the easily accessible connection block, NOT the one buried in the side panel. In the event this block works itself loose, it is as easy to replug as accessing the CD changer. In addition, buying a used wiring harness has its pitfalls because you do not know how carefully it was removed. I was able to find several used tow module controllers on Ebay (mostly from Europe) but wiring harness were rare. I did contact several Ebay sellers if they had the wiring harnesses and all of them said they were not available.
In addition to these three main components already discussed, there are several other small parts needed, as listed in the AFTERSALES literature. Fortunately for me, I have a garage full of the appropriate accessory hardware, however, I verified everything in the AFTERSALES literature is available from our host.
Electrical Connections:
The wiring harness plugs into the SUV in two locations, one very easily accessible, the other one- not so much. The first one is located in the side access panel, underneath the CD changer, against the inner rear side of the vehicle towards the very back of the SUV. In my Cayenne, there were three connection blocks, two were already being used, the third one was green and the green pigtail from the wiring harness easily plugged into this connection.
The second place the wiring harness needs to be plugged into is the tow module controller. The tow module controller then is mounted in front of the CD changer in the right side trunk panel on the passenger side. There you will find wrapped in grey foam is a red pigtail which then plugs into the tow module controller. This assembly is mounted in an already present mounting bracket. The controller is mounted vertically with the connections pointing towards the center of the SUV.
I considered splicing the red pigtail and lengthening it so I could position the tow module controller in the open space below and behind the CD changer, but I decided against it because of potential failure of the various splices. After weeks of researching how to remove the side panels to no avail Wayne posted a motherlode of tech articles on this forum how to replace the rear hatch shocks. This write-up was very well written with detailed photos.
Pelican Technical Article - Porsche Cayenne - Rear Hatch Shock Replacement
However, the process of removing the side panels is a bit tedious so before I tore apart the SUV I wanted to test out the hardware first.
I got lucky, the red pigtail which plugs into the tow module controller was located towards the front of the CD access panel, NOT wrapped in the grey foam as described on the Web. I had the dealer install my XM Satellite radio, and they may have removed the tow pigtail and placed it where I found it. (See Photo)
It was very simple to plug this pigtail into the tow module computer; next I plugged the green pigtail into the green connection behind the CD changer. My wiring harness already had the 7 blade Pollack electrical connector in place, so I was ready to test the system.
Using a Durametric (Version 6) scanner I was able to verify the installation by using this diagnostic tool to identify the controller and run diagnostic tests. The scanner correctly identified the part number and version of the Westfalia tow module controller and diagnostic tests verified the tow module controller was working properly.
END OF PART 1