Hi everyone,
I recently installed a factory tow bar and wiring to my 2015 q7 (4l). All went pretty smoothly but when i hooked trailer up the lights were flickering. Did a scan and found module coding issues. I then got my obd eleven to recongnise the trailer module, updated engine, mmi, parking sensors all to tow hitch installed . i no have no codes and can read the live data in tow module . i hooked the trailer back up and still flickering. The trailer has l.e.d lights. looking back i should have gone bypass relay route but i wanted factory look and functionality. Have i missed something in coding? or is this a trailer issue?
Scar

 

I can’t speak to coding issues but LED lights can and do cause issues with many tow vehicles. Manufacturers are designing around these lights today but even my 2025 SQ7 can’t connect to our 2021 Airstream without triggering a dash warning involving trailer lights. In order to get around this, I simply added a small incandescent in the trailer that is powered by the running light circuit. This allows the Audi to see the current it wants to work happily…

 

Do you have any info on what you added to traiker ?

 

The issue with LED trailer lights is that the tow vehicle is not designed to recognize such low current as being “correct” this can trigger all kinds of weirdness. In my case, my SQ7 was fine with the Airstream’s directionals and brake lights but as soon as I turned on headlights, the car was unhappy and began disabling systems. I added this little Perko, non LED anchor light to the trailer and it provided the resistance/current draw to make the Audi’s electronics happy. You can find any incandescent bulb to wire in temporarily to see if it corrects your cars issues. It doesn’t matter if you add it to a plate light or a tail light or a marker light, the source is all the same circuit in the car. I chose to keep all of our LED lights on the trailer and simply wire this light fixture into the electrical distribution area where it will be out of the elements.

 

Thanks ill try that but nothing works in mine

 

OP, I did same on our '15 TDI...factory tow kit accessory purchased, which has everything except the higher wattage radiator cooling fan & dedicated (better passive cooling /more vented) fan shroud you get w/factory towing option.

I hooked up to a U-haul 6x12' enclosed trailer w/LEDs all around and experienced the same type issue...the led marker lamps all came on, but flickered some, and the brake lights didn't function at all.

I resolved this in two steps.

First I bought the plug-n-play Curt LED light adapter at the U-haul place...it basically has resistors in it to get the voltage use sensed by car in correct range, so no errors in car over bulbs out, etc. Audi sells this same Curt LED trailer lights adapter as an accessory item, just FYI.

Secondly, I found that the new tow lighting control module coding needed to be adjusted to diff region to get the LED tail lamps/brake lights on the trailer to function properly; this was brand-new kit directly from Audi, and so wasn't setup for correct country/region lighting standards as yet. I don't recall which setting I ended up using, but I verified the brake lights/turn signal lights were working on trailer and all led exterior marking lamps were also lit, etc.

After that all was well with the trailer lighting; no more random lighting errors popping inside of car, and of course the 4L Q7 TDI tows a trailer like it was purpose-built for towing...simply spectacular!

 

Thankyou ill try to make myself a resistor box fingers crossed it works

 

As an update to anyone in the future , making a resistor box woth 15ohm 10w wore wound resistor fixed it, all lights working

 

Or you can buy the plug-n-play adapter if you aren't super-handy DIY like that with electronics . I keep my Curt LED trailer lighting adapter in the under floor storage bin with recovery strap and other tow & safety accessories, and it just plugs in between car' 7pin outlet and trailer's wire harness, so I'm always ready to tow. IIRC paid like $16 at the U-haul store, and you can find this Curt LED lighting adapter online pretty easily or even just get the part # off Audi parts/accessories site to search on, etc.

Regardless of how you make the car 'happy', you need to make the control module 'happy' about the voltage draw sensed in the trailer lighting loop, so pick your poison; you got options.

 

They don't sell.those where I live unfortunately, also I made all the other wires pass through so I can tow our caravan without issue hopefully. As its a 12 pin setuo