As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED A - SMOKE TOILET - MESSAGE SHORTLY AFTER TAKEOFF FROM TYS. AIRCRAFT RETURNED TO TYS AND LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE LAVATORY SMOKE DETECTOR AND PERFORMED CHECKS USING THE AIRCRAFT MAINTENANCE MANUAL. NO FURTHER DEFECTS WERE NOTED. THE AIRCRAFT WAS RELEASED FOR SERVICE.