4-Pole Wiring Harness Installation on 2012 Audi Q5

Question:

Installing a Trailer Wiring Harness on a 2012 Audi Q5. I have power working, and the left/right blinker but Which wire is the brake light/ running light and are these combined?? I currently have the red wire to the grey wire with black stripe on the upper tan harness. I have the brown wire grounded.

asked by: Andrew C

Expert Reply:

If you are installing a 4-pole wiring harness kit like # 119250KIT or # C59236 you'll use a circuit tester like # PTW2993 or the one included with the kit to test the vehicle's taillight wiring to find what function is carried on each one. Auto makers are not consistent with wire colors used in vehicle production, so testing is the only way to be sure you are making the correct connections. The linked videos show how to use a tester.

In standard 4-pole trailer wiring harnesses like those noted above the stop and turn signals are combined onto one wire/circuit. The green harness wire carries right stop and turn signals and the yellow wire carries these for the left side. The brown wire on a 4-pole harness output side handles running lights. Ground wires are typically white.

expert reply by: Adam R