You'll be interested in the Freeze Frame data when the code stored. The
OBD-II tester you used may be able to give this to you. A very high
temperature suggests the vehicle was overheating for some reason. A very
low temperature (-40 degrees is common) suggests a coolant temp sensor
problem or an open circuit in the sensor wiring (almost always the
sensor). If the temperature is not at operating temp but not ridiculously
cold, then you may be looking at an issue with the thermostat stuck open.
Do you have the actual code? That may help narrow things a bit.