TQ DGH - FC4, FC5, FC9, FC15 and FC16 Thermistor related faults
Fault code history can be accessed:
SETTINGS/SERVICE/GAS HEATER 01/7378 CONT/FAULT LOG
YouTube Video - MagIQtouch Heater Fault Log
FC4 - Thermistor > 70° during run
FC5 - Thermistor short or open circuit
FC9 - Thermistor > 60°C during start
FC15 - Thermistor in cool duct location
FC16 - Thermistor not installed in outlet duct