I have a P2 controller and it's suppose to be powered all the time. The display will blank out after a while with the ignition off. But even without keys in the ignition, if I manually activate the trailer
brakes, or just step on my vehicle's
brakes, the controller will power on again. It's safer this way, in case your ignition switches off for some reason while you're towing, your trailer
brakes will still activate.