TPS issue and troubleshooting help

[Green67Stepper]

So I got in the truck the other day after not driving for a few weeks and the transmission was shifting into OD really quickly and then wouldn't downshift under throttle. (does downshift when I slow down and/or come to a stop). I noticed on my gauges that my TPS was 0% and the truck was running rough to so I assumed that was my issue. I also had P0122 and P0123 stored codes for High and Low TPS circuit voltage (CEL never came on).

I replaced the TPS and went ahead and replaced the pigtail as well. I first tested the TPS by using my multimeter to test ohms. As I moved the TPS, it varied from 0-5, like it should, with leads on the signal and reference wire of the pigtail. I hooked everything back up and then back-probed the butt splices to test more. The white reference wire is getting 5.1v with key on. With Key off, and the multimeter on continuity test, (one lead on Neg battery and one lead on TPS ground wire) the MM beeps and shows continuity.

So, the issue I can't understand is when I test the signal wire (blue), with key on, and back-probing on the new buttsplice, I get nothing. I know my new connections are good, but can't understand why I'm getting no signal, when my reference wire is good and the TPS tests good.

When I run the truck, TPS% always shows 0% now and once or twice while driving around last night it flashed to 100% for a second or two.

Where should I go from here? I should add, its a 2000 5.3l DBC with a 4l60E. bone stock with a re-worked factory harness.