I've been trying to figure this out also but my situation is different. In my setup I have and HKS CAMP2 running to one of the AUX vid ins. But I can't listen to another source(xm,ipod,cd,etc) and it gets very quite in the car. So what I had to do was hook up that input to the rear vid camera and have it on while the GPS is running. The manual really doesn't explain much and I begining to think the unit won't do it at all .