Check engine with trailer connected

[Beatty, Robert]

Ok,

Talked to dad on this as its something right up his alley (he does alot of
towing and knows alot more about Audi's than I).  

He said the reason you are getting the auto check light is that if you have
only tapped into one side for brake you are drawing more current on that
side and setting it off.

3 things you can do.

1.  Tap into each side brake light/turn signal

2.  Tap into the brake wiring BEFORE it hits the autocheck system.  Thats a
small black box in the trunk on the left side.  Tap into the wiring before
the box and the car wont see the difference in the current flow.

3.  Get a converter box like some others have suggested.

4.  Buy a truck! heheh couldnt resist

Good luck

Rob