I used the P2 on my two trailers for an extended time and then when I got my new 2010 Ford truck it came with an OEM Brake Controller. I sometimes wish I had the P2 again.
My OEM FORD BRAKE controller by design does not work when using the brake pedals when I am below 9MPH. I have to use the manual slider when moving below this low MPH speed.
The part I miss is when being stopped at a stop sign on a decline I have to use the manual slider to hold my trailer brakes ON.
I almost think you have not setup your P2/P3 correctly as like said above there is a whole bunch of us out here that really likes the P2/P3 brake controllers.
Roy Ken