After searching and pouring through the inter-webs, reading argument and counter argument about installing a break controller, I decided to write a complete guide of my own. This guide is for Touaregs with the factory installed tow package. These, despite many rumors, do have the brake control wires pre-wired. Some cannot find it, but it is there. I installed the Tekonsha Prodigy P3 brake controller. First, find this little plug hidden in the bowels of your dashboard. Two size 20 star headed screws hold the cover in place under the driver’s dashboard. Once the screws are removed, pull down sharply toward the front. Two metal friction clips hold it in place. Pull down a few inches and undo the OBDII connection by squeezing the clips at the top and pulling up. Now pull the panel toward the driver’s seat. This will free the panel from the two clips toward the firewall. Open it up enough to unclip the foot light, then completely remove the panel. Now you have unfettered access to the wires you seek. Lay on the floor as best you can and look up. Follow the parking brake release cable. It should make almost a 180 degree bend. Look up from the apex of the bend, and against the outside wall. There is a grey foam thing sticking out of a black wire loom. This is your quest. Grab that grey foam and peel it back like an uncut…well, look inside. If at first you don’t succeed, pay a 14 year old boy a dollar to find it. It will take him 30 seconds. Trust me.
Now you feel confident to order parts online. A few different sources offer the parts. I ordered mine from ECS Tuning. What parts you ask? Google “Tekonsha TB 0021” and read the instructions. It states 2005 to 2008, but it is verified accurate until (and including) 2014 models.
The next step is to find a four pin 12 volt relay. This is because there is a constant voltage bleed through the red/black brake light wire on the Treg. This will cause a constant slight brake drag on your trailer…and decreased gas mileage! So the relay takes 12 volts to activate the controller. That’s as simple as I can say it, other than trust me. I found this relay at a local auto parts store. It also had the socket with four wires it plugs into. This made wiring it easy.
To build the wiring harness, grab the harness from the brake controller, the relay and the plug for the Treg. The instructions walk you through the process fairly directly. What it doesn’t show you, is that you can draw power and ground via the black (2) and white (1) wires. This way the entire harness can be unplugged when not in use. Follow TB 0021 to the letter. Note that the ordered harness for the Touareg is numbered, as is the plug pre-wired in the truck. However, double check the wires going into the prewired plug, they have been known to be in the wrong order. I wrapped my bundle in friction tape for a cleaner look. Plug it in! Now look for a place to mount your controller.
This is where things get interesting. I chose the far right side, as it seemed the least in the way. I moved the seat around and played with the location for quite a while. If you too choose this location, the mounting bolts become difficult to control. The screw on the right side of the metal to plastic isn’t accessible if the metal portion is mounted first. However, if the metal portion is mounted to the plastic clip first, you cannot access the screws to mount the entire piece. Rather than using the supplied screws, I used some leftover VW bolts and nuts. This works great if you don’t want the mount always there. However the nuts are a pain to get in place. Therefore, I added a bit of moleskin to the back of the metal bracket to prevent scarring of the dash. Yes, the dash that I just drilled holes it. Don’t mock me.
Did this explain things? If you have any questions, I’ll do my best to answer. i did take other pictures, but I thought this was enough. I'd be glad to help anyone who wants to take this on.
I read that post before wiring up my TReg as well. I called Tekonsha before install, and they said that after more testing, the voltage bleed from the TReg varies based on the electrical use of items bundled in the same loom. This has to do with electromagnetic lines of flux and the types of shielding VW uses. This can cause the voltage reading to the brake controller to be greater than 4.3 volts (which has been programed into the controller to as the max bleed voltage), therefore causing the brakes on the trailer to activate.
I figured spending the $7.00 was a minor expense to alleviate this issue.
Some may be wondering about the battery drain when leaving the brake controller connected. I left it in the car for five days and no appreciable drain was detected. It seems to go to a standby (practically off) when the car is turned off.
For those who think it forgets the settings when unplugged, the P3 does not. It retains the last setting when plugged back in, meaning it has nonvolatile memory. It also has three programs that can be saved. So if you have three trailers, you can program and save the settings for each. If you have a horse trailer, you can set it for empty and full.
I have a 2008 V6TDI fitted with Horizontal tow bar and P3 controller. I have just bought a 2012 with factory fitted vertical tow bar and factory wired for 7 pin plug. My question is should I transfer the P3 over to the new vehicle. Wouldn't the factory wired plug control my trailer brakes OK?
I'm not sure what the vehicle and horizontal hitch is that you are referring....but...
As long as the controller wire loom ends with the factory four pin plug, you can swap it back and forth. I swap mine between the Audi and my VW. Double check the wire colours on the factory plug, as they are known to be missed wired at the factory.
Thanks for the reply 47Driver, I rephrase the question. If my Treg is wired up (7 pin plug) and factory tow bar, why do I need the P3 controller. Does the Treg have inbuilt brake controller? or is it just wired for lighting and an unbraked trailer? Then I require the P3 for brake control.
In other words there is no trailer brake controller fitted to any Touareg, but the wiring is in lace to connect one easily. (Except I have never been able to find mine GGRRRRRRR) John
Great write up. Found my plug in 10 minutes. 2012 Touareg. I have read the nightmares of dealers spending hours upon hours trying to find it with no luck. I spent 10 minutes because of your info. Thank you fine sir.
4D, I was thinking of mounting my P3 using an extensionpiece of flat metal on the mounting bracket. Is there anything of substance behind the dash? Also I am worried about drilling through anything important.
I just bought a Treg 2011, the first proprietary of the vehicule had installed a brake controler has shown in the precedent post. I think he cutted the controllers wires before to sell the car because the color of the 4 remaining wire fits with the cotroller wires. I bought a new controller connector and connected it to the cutted wires. I plugged my Tekonsha Primus IQ but it dosent work. No light, nothing. So I checked the voltage onto the plug: Nothing. Then, I checked the voltage into the buildin Treg square brake connector: No voltage. Yes, the car is running. Is the 12v supposed to be always on? Do you have an idea why there's no voltage?
Thanks!
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