As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE THE APU OIL TEMP CAUTION MESSSAGE ILLUMINATED. THE CREW FOLLOWED THE QRH AND, DUE TO A RT IDG MEL AND WEATHER AT BNA, DIVERTED TO TYS. MAINTENANCE REMOVED & REPLACED THE APU HIGH OIL TEMPERATURE SENSOR. THE APU OPERATIONALLY CHECKED GOOD. THE AIRCRAFT WAS RELEASED FOR SERVICE.