Six cars after getting the dyno up and working, this happened. We were loading the 7th car on the dyno that Saturday, and I was going through turning on the computer and the electronics as I always do, when I clicked on the make run screen, nothing happened. It said no communication. So after about an hour or fiddling with cables, trying this and that, I realized it was the stack that was at issue. It was all green, but no yellow comm lights were flickering. Shit.