Looking really good step!
For the DD fuel sender. The instructions say "recommend" you run 2 wires back to sender. I did not do that and it works pretty accurately from what I can tell.
1. I ran the 1 wire back for data connection on sender.
2. Sender grounded to frame.
3. DD sender ground connection(I just ran this to ground buss in cab via the AA wire harness.
I have ran the tank empty couple times, put in 5 gallons once, put in 10 gallons another time, they all read correctly. I think the issue is ground here. If you don't have an excellent ground, resistance and/or noise on the grounds could make the gauge not read correctly(like when your radio isn't grounded well and you hear engine rev in your speakers). Using twisted pair helps reduce noise on those lines.
I won't say this is perfectly spelled out here, someone can correct me if needed, but you get the picture. Check them grounds!
