How to trick Car's Computer Into Trailer Attached Mode?

2008 A4 B7 Avant

Is there a way to activate the car's computer into tow mode when using a bypass relay for lighting? The computer has been enabled for towing, but by using the bypass relay instead of the dedicated Westfalia towbar wiring harness, the car won't know when a trailer is attached. The Westfalia wiring is still in place, but the trailer will be connected to the bypass electrical connector.

Thoughts?

Thanks very much for your response.

I also have the dedicated Westfalia towbar wiring harness installed and have enabled the tow module in the computer by entering the code. Additional background on my scenario can be found here. Is there a crossover wire I could add to the Westfalia tow bar plug, or somewhere else, that activates tow mode as needed since everything else is in place and coded correctly?

I seem to be the only person in the U.S. that has come across the issue with the Westfalia harness and/or is trying to leverage the towing capabilities of the A4 Avant via the computer (which I find hard to believe).

Thanks!