Thank you for the offer, and I'll take you up on it. I have one code on my truck; P0463. I'll give you the history of it, as it might help in diagnosis. It's a 2005 5.7 with manual transmission.
Almost to the day, my original fuel pump went out. I had it replaced at a mechanic shop two blocks from where it stopped running. Everything was fine for two or three months and then the gauge stopped working. I figured they installed the cheapest fuel module they could buy. As the truck otherwise runs well, I decided to run it for a while to get my money out of the repair.
Last weekend, I replaced the fuel module. After the pump primed, it started fine and otherwise is just like it was the day before I did it-reliable, but no functioning gauge. I did the cluster test and the fuel gauge sweeps, so I think I can rule that out. The idea that I got a crap fuel module is possible. I didn't test the sending unit before installing it. Yet I can't quite buy into the sender also being bad on this pump, also.
Putting the possible issue of a brand-new sending unit defective out of the box (we can come back to that, if needed), there's just wiring, I think. I have the wiring diagrams and as best I can make out, the two center wires on the fuel module harness are for the sending unit. One is BL/GN and the other is BL/RD, IIRC. The BL/GN should be the ground per the diagram.
I followed these wires back to a large connector on the frame directly below the firewall. I stripped half of the insulation on the BL/GN wire midway betwen that connector and the tank and made a temporary supplemental ground to the frame. Nothing changed.
Any ideas of what to look for would be appreciated. Thanks in advance.
EDIT: Wires are BL/GN (sensor ground) and BL/WT (sensor sender) per diagram.