If your getting voltage to the controller and gave a good ground and still nothing (display or any signs of life) its a gonner. Had my P2 for 2 yrs and never had any issues. If its a random issues with it not operating correctly and all your connections are good, just replace it. I wouldnt want to rely on it in an emergency not knowing if its 100% functional or not.
*Currently trailer-less but shopping
07' GMC Envoy w/ P2 controller (current TV)
88' Chevy K5 Blazer (soon-to-be TV)
74' VW Superbeetle (1303)