Follow up Part 2.
After seeing this I decided I would cut the 2 wires out of the loom and replace them with the salvaged wires. I had about 8" of wire to work with on the salvaged units, so I staggered the cuts of the 2 wires so as to not have a couple of heat shrink tubes adjacent to each other. I did "one wire at a time" and used "strip-twist-solder-heat shrink" method to join and seal the wires. I connected the harness back to the ECU and started the engine. MIL went out after starting and no codes were showing in memory. I taped up the loom and then drove the truck around outside making sure I visited some of the "rougher" areas of pavement for about 20 minutes and so far it has not missed a beat. After the successful test drive I took one of the faulty terminals I snipped from the truck harness and placed it onto a pin from the original ECU I took off the truck. Turned the ECU upside down and the wire just fell off. I extracted another wire from the salvaged ECU connector and repeated the move, this wire stayed in place and would not fall off even when I shook the ECU up and down. Monday I will report my findings to the manager (including the shake demo) and suggest that this truck really should have a new main harness before it is to be considered trustworthy.
This has been a hair pulling "ordeal" in a lot of ways. We received the truck with absolutely no historical information as to problems it may have had, that nobody had ever resolved. There was plenty of reason to think this truck has spent a great deal of down time in somebody's hands, judging from the complete disarray of the truck wiring from front to back. We probably found at least one of the defects that may have been haunting the truck's OPSS (KOPS) system, and that issue may be what ultimately led to all the truck's other issues (except the O2 sensor) with DTCs. This defect that was found was damage to an unused, 3 wire connector near the base of the left rear FOPS pillar. This connector is used to outfit the truck with a "back-up alarm" or a "travel alarm" if the end user wants to have notification that the truck is moving Forward as well as Reverse. The plastic connector body was broken on one side and the BLUE wire was hanging outside the connector. The blue wire here is common to the transmission Forward Solenoid valve and is fed from the Forward Relay. The condition of the metal terminal showed that it had at times been shorting to ground as most of the terminal was eroded away. I suspect that the shorting (even a slight brushing type of short) may have been popping fuses and/or causing false operation of the KOPS system, and fruitless attempts by someone to resolve that issue may have contributed to the damage and destruction to other components in the truck wiring. I can only wonder how many times various connectors (including ECU) had been separated, sometimes by force, in their poking and prodding. But I am near the point of closing this case pending my conference with boss Monday.