E09 is not in the Manual, and is rare, but it is an electric voltage or frequency protection for the Motherboard to wired Controller. When the power goes off or outside minimum voltage during a storm seems to be the trigger. When the power comes back on the Controller will display E09 as the condition. It is more a record or warning the event happened, it could be taken to mean the home should consider voltage protection device to avoid damage not covered by warranty.
Resolving E09 is to turn the breaker off, and on again to reset the protection. A couple instances have been seen on Vancouver Island and line up with wind storms. Chico Electronics reserves this spot as a non-serviceable item, and unfortunately elevates the default to prevent initial start up when the power is restored resulting in a manual reset to make the condition known.