It's not as simple as the low voltage to the tps. That's only part of it. Even if the tps had adequate voltage the ecm still has to do the calculations and ground the od solenoid. If the ecm is dead the low voltage is only a part symptom.
When I went through all this a month ago I did the pinout checks that you've done and the one I suggested to confirm the grid heaters were working. I also stuck a 1/16th cotter pin in the #55 terminal and ran a wire from it through the firewall and left it hang by the steering column. Drove the truck to speed and grounded that wire against a dash screw. Shifted into od. In as much as all these functions went out together, cruise, grid heaters, and od, and actuating the heaters and od by grounding their respective pins in the plug caused them to work, and all my inputs tested okay I went with the assumption the ecm died. Pulled it out and had it repaired. Installed it and my diagnosis was confirmed.
I couldn't drive it without od, 4.10 gears and highway ride to work. Also too cold to start without grid heaters. So while the ecm was away I wired the #55 pin to an on/off switch that grounded it in the on. I Used cotterpins and connected the two grid heater pins to a wire and ran it through the firewall and just let it hang.
Go out in the morning , turn the key on, ground my heater wires for about 15 seconds and twist her tail. Operated my od with the switch. Lived without cruise.