Trailer wiring - AudiWorld Forums - Audi News and Discussion Jun 07, 2010A4 (B7 Platform) Discussion - Trailer wiring - Has anyone wired for a simple trailer on a B7? I want to tow a small trailer with a 4 prong lead (brake lights and turn signals). I assume that the extra power draw will freak out the can-bus if not done right?? Audi A4 Trailer Wiring | etrailer Guaranteed fit Audi A4 Trailer Wiring. Lowest price guaranteed. Thousands of customer trailer wiring reviews, expert tips and recommendation. Lowest price guaranteed, easy online ordering at etrailer or call 800-298-8924.