This can be found via various other threads, but I had to scroll through to find.

If you are trying to setup the Advanced Towing feature, the setup feature will not work unless your Discovery recognizes your trailer when you first turn on/connect the trailer. With my daughters horse trailer the LED lights are not enough to trigger that connection. You can buy Sylvania "Load Resistors" at Walmart, Advanced, Amazon etc. You connect one end of the resistor to the load on each of the blinker load wires on the trailer and other end to ground etc. You will know this is working immediately, when you turn on the blinkers with trailer attached, and see the trailer icon blink in conjunction with the normal blinker signal.

As soon as I did this the Discovery will then recognize the trailer at startup and it will then allow you to proceed through the advanced towing trailer setup etc. Without the Discovery recognizing the trailer first it will allow you to go through all the steps of setup, but will stay on the yellow screen, and will NEVER turn green for you. You can try all sorts of sticker positions, lighting etc. but the car will not turn green recognizing the sticker etc.

Finally I may be wrong about this, but I believe you may want to turn your turn signals on when starting your vehicle to help it recognize the trailer is attached. I had 1 instance where it did not recognize the trailer during two startups, but by activating the blinkers it did.

Hopefully this will help someone else with the headache of setup.

 

I added the resistors to my travel trailer which has LED lights, but you cannot rely on the light flashing on the dash to confirm that the tail light is still functional. Not a big deal, just make sure to do a light check.

 

I put resistors across both stop and tail lights. The Disco recognizes the trailer every time.