I've installed a trailer hitch on my 04 TL to tow my motorcycle. (It's an 800lb total load. And yes, I've read that it's not recommended).

For the wiring harness, I went with a T-One connector from e-trailer. http://www.etrailer.com/pc-VWH~118489.htm. I'm only going to tow MAYBE every three months or so, so I wanted a harness that can be easily removed.

The T-One harness essentially parallels off of the existing turn signal and brake circuits. The trailer lights are all incandescent. The turn signals work fine. But with the trailer parking/brake lights paralleled with the car's brake lights, no illumination occurs. Then if I hold the brake pedal down the "VSA" and "!" lights come on after approx 3-5 seconds, and stay on. The lights are cleared when the ignition is turned off and turn on again.

I haven't had the time yet to troubleshoot what type of supply voltages I'm getting through the harness for the parking/brake lights. But my real question is:

How is the VSA system tied to the brake lights? I've tried to find the electrical wiring diagram but haven't found a free one yet...

And here's my stupid quesition... What fuse protects the brake lights?