I have a 2005 Excursion 6.0. After recently servicing all 8 injectors, the turbo, and the HPOP due to a crank/no start issue, I drove it for two days until the EBP sensor failed. I replaced that, but the next day it died right after leaving the driveway. It would crank once and then die as soon as the engine tried to start.
I ordered a new PCM after seeing all the bus failures and because mine seemed very hot, which I assume caused it to short. With the used one I just installed, I am getting the issue shown in the picture.
I partially disassembled the lower dash and loosened the fuse box. I checked the fuses that seemed relevant, and they all appear fine. What should I do next? Should I disconnect and reconnect all the harness fittings on the other side of the firewall?
Finding the power and ground pins on the ficm/pcm is the first step. Then, you should check the power pins for voltage availability, disconnect the ground connectors, and verify that there is continuity to the battery’s negative terminal. The PCM will not function without those two items.
U1262 in the system indicates that the security system is not communicating with the PCM, which suggests the PCM might not be present.
You could be dealing with a faulty PCM or a connection issue. Since the problems began right after recent injector work, check around the valve covers for any pinched or improperly connected components. It might also be a malfunctioning FICM, which can block data lines to the PCM if it fails. It is not unusual for a FICM to fail soon after installing new injectors, as they are sensitive to changes in injector resistance.
I have partially removed the lower dash and loosened the fuse box. I checked the relevant fuses, and they appear to be fine. What should I do next? Should I unplug and reconnect all the harness fittings on the other side of the firewall?
Fantastic information, man. It’s a reman FICM, and for peace of mind, I have been considering just ordering an Atlas 40 tuned ficm. 
You installed a used PCM/TCM. How can you be sure it’s functioning properly?
Try reinstalling your old one and check what the same screen displays.
I purchased one from Chattanooga Diesel Tech following their advice. It has passed inspection and testing at their location.
Yeah, that makes sense. However, did this problem also affect your previous one?
Making a decision about the diagnosis’s future course is important here. It could be a harness problem.