if disconnecting the coil kill wire(s) stops the problem, if the repair cost is too high, could one add a kill switch toggle, label it and use that when shutting down the engine? In my mind's eye, anything that might trigger a shutdown in the logic could be the failed component. For example, let's assume for now that the ECM sends a kill signal when it is told to shut the engine down. If the ECM goes bad it could do that as a failure - but if say a safety switch is going bad, it could be sending an unwanted signal to the ECM to shut down. I think the advise to buy the manual is the path I would take. It is possible that more than one safety switch is involved, or even a connector that is corroded. Meaning - let's say the ECM expects 12V on a certain pin when it is safe to run, if there is a corroded connector that causes that pin's signal to go away then that could cause it. Unless one has the manual to detail the logic the system uses, I think it would be quite time consuming to dissect how the system is supposed to work electronically.