Truck immediately fires briefly each time the key is cycled and an attempt made. It does no good to keep cranking. It is shutting down electrically after less than one second each time. I know this because the scanner loses communication at that moment.

So far I have swapped IDM's and ECU with and without chip.
I also swapped the two main circuit breakers under the hood.
When I run KOEO, the only codes are p0605 with chip and no codes without chip. (typical)
I have changed the CPS (a few times) and the CPS pigtail.

Any ideas?

 

Check fuses of all sorts to start. Do you know anyone who has a truck compatible with yours if so try swapping ecu's or fcim