You need to install a brake controller. The 4 pin connector is under the left side of dash, wrapped in grey foam and somewhat hidden. Sounds like you need to get your tow module software updates to work with LED lights. Tow module is behind the right trunk side panel. Most aftermarket scanners will not connect to the tow module. Need VCDS or similar.

 

I decided to use a “Tekonsha Prodigy RF Electronic Brake Controller” instead of mounting anything to my interior.

Especially valuable when towing same trailer with more than one vehicle, as all you need inside is the remote brake controller (RF, not Bluetooth) that is powered by a 12v socket. The weatherproof controller is located on the trailer, is rather large but extremely durable. After using it for the summer, I highly recommend it.

 

Thanks Chewblekka! when I got the treg used there was a tow hitch and a 7 pin plug at the back, but I don't know if it had ever been set up to tow a trailer with brakes. I had already found the connector under the dash and installed the controller. When I use a 7 pin tester at the back of the truck the light are all blinking crazy.
If I use a test light on the back of my truck I get trailer brakes, left- right turn. When I plug the trailer in only one left turn signal works. I took the panel off at the back right side and didn't see a module. I may not have looked in the right spot but I think I was in the right area. I'm suspecting there is no module, so I would have to get the module and also have the computer coded for the trailer brakes. I think this is going to add up quite a bit (if I can even get a module} so was trying to find a way to determine if that was the issue. a friend has a "blue driver" scanner but not sure if it will work on the trailer brake coding. oh, by the way my camper trailer has conventional lights(2011).
Thanks

 

This is what you are looking for, pic is from my RHD '08.
Module on mine is approx in line with the aux 12vDC socket

TonyB

 

Thanks a bunch Tony! now that's got me thinking I need to take some more panels off. I took off the bottom rear panel that just pops off. I saw an empty plug thinking that may be where it goes. it looks like it's located under the upper panel so I'll have to go and explore further. Thank you for the pic, that helped a lot. Any tips-tricks to get that panel off?

 

No, not really.
To date I've avoided taking that biggest panel off as there's a whole bunch of things starting at the C piller and going back to under the side glass onto the hatch.
Here is the erWin file on interior trim removal, you're gonna need it.

TonyB

 

Thanks again Tony! I'll get at it again and see if I can get a good look in there.
I see there are a lot of variables on the last letter in that part....L,N,M wonder if that will matter if locating one as I see many sources list "no longer available"?
I starting to wonder if getting a wireless brake controller would resolve all this.
Would you know if the computer would still need to be coded when using a wireless brake controller?
Thanks

 

No coding needed for a regular or wireless brake controller if that module isn't there. That module isn't needed, but if present and coded in, provides changes in the way the vehicle handles and drives when a trailer is connected.

 

Thanks for your input C-ya. This is why my head is spinning. Numerous posts say it needs to be coded, that module is needed, etc. I'm still not sure where to go to get the straight goods.

 

By all definitions you do not "need" the tow module installed, but I am telling you that not only will you be leaving a ton of tweaks and performance off the table due to not having that module, but in my opinion it wouldn't even be worth Towing without the module.
With that said if you don't have the module in your passenger kick panel in the hatch, you'll have to purchase one and then pay for it to be coded. If you are Savvy, I've heard of people quoting at themselves with vag-com.

 

You need to understand that the tow module and the brake controller are physically two different items of hardware.

The tow module makes vehicle stability and performance changes to your vehicle when it detects that a trailer is attached and needs to be programmed once the module is fitted, it is always supplied when a genuine VW tow bar is ordered.

The brake controller is just that, it primarily applies trailer brakes proportionally to the amount of brake force being applied by the towing vehicle and also allows the driver to apply brakes to the trailer indipendently of the towing vehicle, the controller is not supplied/fitted as part of the OEM tow bar it may or may not be require to be fitted depending on your states particular towing regulations.

TonyB

 

Thanks to all, I think I'm heading in the right direction. I checked under the right rear panel today and indeed I DO have a module installed already. I called the dealer to ask them and they said that some older Treg's come with hitch, 7way and module, but may need to be coded for trailer brakes. Made an appointment for a week from now (they are busy) to get it coded for $123. I'm not overly confident it will end there but I sure hope so.
I understand brake controllers and have one installed. It's looking like a coding issue with the computer at this point.
anyone know if any aftermarket scanners can code this?

 

I’m sure you thought of this but you didn’t mention it so I thought I would ask. Did you test with a load tester?

 

Thanks Vegastreg. I didn't try a load tester as in a meter. I connected my trailer which is the actual load and found that my brake controller activated the trailer brakes so my brake controller and trailer brakes are working. it's the lights that are weird. Only left turn signal side light comes on ( not rear turn signal), put on right turn signal, and only LEFT side turn light comes on?, right side doesn't come on at all-turn, running, emergency,. If I check the bulbs at those lights that don't come on when they should, the bulbs all work when I check them?
So either I have some screwy wiring problems on the trailer, or the computer coding needs to be done and this is the symptom I'm not sure.
Does anyone know what the computer coding actually does?? ie. does it activate the brake portion of the 7 way plug ( because mine is getting power through brake controller now to rear of tow vehicle. Does that mean this one is coded properly or is the coding more to do with the lights and extra draw on the electric system?

 

I don't know the answer to your question but FWIW, I would be very surprised if the brake controller needs to be coded for it to function correctly.
My money is on the trailer wiring, I seem to recall that the side lights do not each have a separate circuit, did a quick search and found this for you...

Trailer Wiring Diagram – Lights, Brakes, Wire Connectors, & More

Need a trailer wiring diagram? These wire diagrams show electric routing for trailer lights, brakes, aux power, breakaway kit, and connectors.

mechanicalelements.com

TonyB

 

Nice find Tony. One of the best simple diagrams I've seen.
(Are you still towing that floating caravan?)

Pommystuart

 

Thanks Tony, from what I understand from all the searching about this coding matter, I thought it's the towing control module 7L0907383L that's mounted above the rear right tire wheel well behind the auxiliary power outlet that needs to be activated or coded, but perhaps it involves recognizing the brake controller as well. The dealership said that when factory hitches are put on the company automatically puts in the control module but it may not be activated for trailer brakes, just the common flat-4 plugs. I've tried powering the trailer with it's own battery (it's a travel camper trailer) and couldn't get anything going so there could be issues with the trailer. I wish someone around had a good working truck plug to test the trailer with. Either way I'm going to bite it and take it to the dealer/stealer to program and hopefully at least get the truck side working properly and then tackle the trailer if still no go. will check in. Thanks

 

Sounds to me like the dealer is either having a lend of you, or is clueless! If the car already has the trailer module installed and working ( to some degree ) then it doesn't need coding/re-coding.
Your problem is either the trailer wiring is dodgy, or the typical led lights issue. The trailer module needs to sense a certain amount of load before it recognises a trailer is connected, using a meter or test light will not be sufficient to do this ( typical symptom is the flickering )

 

Eddieboy.... It's probably not the case.. but a lot of trailer light problems stem from not having a good ground connection between the trailer the towing vehicle..it's pretty simple to test with a longer single conductor wire with an alligator clip on each end . Make sure you connect to the trailer frame in a spot that is unpainted.. (or a screw head) and somewhere on your car's chassis.. It may do the trick. I've got a couple of boats that I haul with mine.. the larger pontoon boat works great but the smaller fishing boat has LED lights that "flash" when it's connected.. It's no big deal to me.. so I've never had it diagnosed... YES.. light issues can drive you nutz.. LOL.. good Luck and let us know what you find..

 

If you have a Tekonsha P3 brake controller, it will gripe about a bad connection/no trailer. It shows voltage when the connection is correct. If only one side of the trailer is not lighting, I agree with another poster, it must be the trailer wiring, likely a short or break somewhere along the chassis where the wires are routed.
My 2013 will gripe on the MFD . "Check Brake Light" if I remember correctly, if I have a bad wiring contact, with the trailer connected. If I have a bad 7 way plug connection (it has happened with corrosion) then "NO TRAILER" appears on the brake controller display. A good way for me to tell is to try and open the tailgate after connecting my trailer. If it opens with the power actuators, I have a bad connection. The trailer module can see a connected trailer and it shuts off the power lift gate feature.