Ok looks like u have a communication problem between the SCPU and The CPU. Does the truck have SAS? Check the PS contactor next to the F3 Fuse if that contactor dose not pulls in quick enough it will cause that code do u have a wire diagram? because if its not that contactor u will have to check voltages between the CPU and the SCPU sounds like a wire break but may be earthier the CPU or the SCPU