6LCHEVYZ71

So I keep getting code P0452 (twice), Evaporative Emissions System Voltage Low Input, and come to find out, on top of my fuel pump assembly, there is a 3 wire plug just chillin there, not plugged into anything. It has a gray, green, and black wire. Cool! easy fix right? Just plug it in.

I go to plug it in and there is no plug to plug it in to! I have felt on top of the pump assembly and also used a mirror and there is only one plug and fuel 3 lines. The plug that's being used I'm assuming is my fuel pump and fuel sender wires. WTF??

I'm assuming that at some point in the past someone replaced the pump assembly with a different one without that sensor? Is that possible or am I just crazy?? Any other option other than to replace a perfectly fine fuel pump with another pump assembly (that has that sensor)? Truck runs great & fuel gauge works but the Service Engine Soon light drives me nuts! HELP!!