My Ascent has a trailer hitch that's been factory installed and I added the proportional brake controller on the factory wiring harness. It all works well yet the RAB and warning controls could be far better. I hit the RAB button on the dash and the rear sensors are mostly off yet from time to time, the brakes slam on while backing the trailer in reverse. The warning patches on the video screen still work as well. If I turn the features off from the back-up screen, all's well, until I switch out of reverse. Reverse again, I need to disable the RAB from the screen and the warning patches. It works yet is clumsy. Other manufacturers use the brake lead to the seven pole plug on the trailer hitch to sense existence of the trailer. I'm surprised Subaru hasn't included such a feature as well.