rap

we finally swapped the ecm from another truck and it started. my question is what went wrong. someone please give me some hint, can the ecm be repaired.

We did a clutch job after which we did a test run and everything was fine,only to comeback the next morning and it won't crank at all. The display diagnostic can't read the engine ecm(operation failed) and the VECU and cluster give psid 200 fmi 9. We put the starter, relay and key switch on another vehicle and it started fine. I need help on what to do next because I don't have any schematics.