I have had 2 different no spark problems over the years, on was the power transister on the coil bracket and it was replaced then a few months later the ECM was bad, I just got around to installing the ECM today and all is working wonderfully. I also found that the ECM is actually what killed the old power transister because it was fluctuating too much for it. Oh but they did act differently when they went out though, when the power transister went out it would intermittantly have issues then never started, when the ECM went out it was just went somewhere, stopped the truck then went to restart and it was dead with no spark...

I hope this helps...