Electrical problem
2001 Chevy Silverado V8 Two Wheel Drive Automatic 104K miles

A couple of days after replacing the fuel pump in my Silverado 1500, the service light came on and I checked/cleared code P0452 evap sensor low. It came right back on about two minutes after starting the engine. I suspect it is one of these two things: (1) bad wiring connection
(2) bad sensor in new pump. I tend to think it more likely 1 than 2. Any other causes I need to check out?

Thanks!