Fuel gauge wiring?

Good afternoon, I'm looking for some information on how the wiring for the fuel level sending unit. Specifically, I'm hooking up an aftermarket fuel gauge and need to know how the factory fuel gauge/sending unit works.

From what I see in the wiring diagram and on my truck, the Fuel gauge sender wire is Yellow, from here it looks as though it goes into the antislosh module, which I no longer have. I do not seem to have varying voltage from the yellow wire, as I slosh the fuel tank back and forth, which I had expected to get.

Thanks for any information you're able to give me