Tow the bus home, stop throwing money into their pockets! They either know how to troubleshoot or they can suck you dry while they learn on your dime!
Once your home, see if you can either borrow another ECM or take you ECM out and have it tested in another bus or send to a shop for testing.
I also posted in your other thread a video link. It covers a CAT - Crank but no start scenario.
ALSO... by utilizing the forum search button I found a thread that answer your question.
Repair Manuals and Info for Thomas Saf-T-Liner MVP buses