Just watched a YouTube video on the installation of a Prodigy Brake Controller. When the tech showed how the display shows "0.0" at the minimum power setting, it dawned on me that maybe the car wash guy turned it down. I checked it. Sure enough. The power wheel was rolled full back toward the rear of the truck. I hooked up the truck to the fiver (wiring only) and stepped on the brake with power set at minimum. Got "0.0" reading. Rolled wheel forward to full power and got about "3.7" ....without even moving. So I guess I diagnosed this non-problem.
Maybe my stupidity will, in the future, help some other frustrated person who is ready to leave home, in an hour, when this happens.
Ain't the internet great?