Ignition bypass mode

[89Formula]

I believe my ECM is bad. It keeps going into/out of ignition bypass mode. I have been trying to isolate this intermittent problem for months, I have had the ECM in my floorboard, where I can monitor different sensor inputs. Found out last week if I bang on the ECM out of frustration, the problem clears up. Today I found the Ignition Module Bypass line toggling, normally high, 5v, then low, 0v, when engine acts up.

What does it take, what has to go wrong, for the ECM to enter ignition bypass mode? Is bypass mode high or low? I beleive bypass mode is low, but engine runs horribly this way, misses, erratic RPMs, exhaust smells terrible.