Reply by Williams Int.
Due to the cold weather, the microprocessor can cause the indication you saw on both aircraft.
We recommend turning the battery on for a minute, then turn it off and then to cycle power.
This procedure is located in TASK 71-00-00-760-830 "General Operating Procedures" of the FJ44-3A-24 and FJ44-1AP Line Maintenance Manuals. If you scroll down to number "6. Abnormal Operating Procedures", it states that if the FADEC is below -40 degrees Fahrenheit at start up, it may need to be power cycled after being turned on for a minimum of 3 minutes to reset it's microprocessor.
As you said after a while having the power turned on, the indication disappeared. We recommend operating the engine AFTER the indication has disappeared so that the FADECs operate properly due to the cold weather.