Good question there are three wires comunicating with the computer, the pip out #6 is the same as the camshaft position sensor signal to the computer. the spout in #5 is how the computer tells it when to spark unplugged the timing is fixed. I am guessing the pip voltage is different coming from the computer telling the hall sensor when to switch the coil #2 coil neg. The other three are power run/start and ground. I was just reading my chilton the leading edge of the vane turns on the coil and the trailing edge switches it off creating spark in run mode or dwell, on start mode or push start mode it only uses the leading edge for spark or base timing. If the computer or spout it interrupted it always reverts to base timing no dwell (limp mode) If the engine runs without the spout connected and the dizzy and ICM test good it is likely the computer or a wire that is bad. I find it amazing this all happens at 3 times the rpm or at 2000 rpm the coil switches on and off 6000 times per minute plut it controls the dwell angle and injector pulse length according to engine temp, rpm, air temp, barometric pressure, O-2 and throttle position did I miss something.