I couldn't find a diagnostic flow chart for my specific furnace and took a chance as it costs at least $100 bucks to get a tech to do a housecall plus downtime from work and a service call quickly costs $500 bucks just for diagnosis. I'm no stranger to diagnosis as I work as an automobile tech and have to logically diagnose problems all day. The problem was I couldn't find any test values anywhere for the smart valve vs. motherboard I had traced the problem down to either one of those.
I read and re-read all the threads about the frequency of failure of the honeywell smart valves and decided to buy one and take the chance. I figured it would be cheaper buy the part and install it than getting a furnace tech to come to the house.
Got the smart valve in the mail yesterday, installed it after work last night and had heat within 30 of walking into the house! Last night was the first really cold (for here) night and we had heat in the house! whew, what a relief, I was getting stressed about the prospect of not having any heat this winter for any prolonged period of time.