I would also like to know. I have just gone through the same exact thing with my ty. Check engine light is on, but no codes. Tested ecm in another truck... works fine. Wires and harnesses LOOK ok, still won't start. I also have my battery disconnected while it sits overnight and figured that would rid my truck of the problem (as far as reseting that invisible code), but it doesn't. Only difference between mine and his is that mine won't fire up, just cranks. Somebody has to know...
Jeremy