I would check out the solenoid itself, helpful when you have a professional scan tool that allows solenoid activation. Another thing I would look up is TSB, because I recall there being a TSB for the EVAP canister issue on these vehicles. Certainly by now that TSB would have been satisfied, as I am sure this thing as seen a dealer since the TSB. Always good to check though!
A good indicator is if you smell any gasoline around the vehicle. The slightest hint of gasoline odor means there is a leak. Sometimes you may smell it sometimes not. I have noticed from experience that older vehicles will have a tendency to give off a gasoline odor in the summer, but not in winter. Makes sense since the heat of summer really causes the gasoline to evaporate, and the pressure builds up and causes leaks at old seals.
So just be aware of that and hopefully you will find out what's causing this.