As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SMOKE TOILET CAUTION MESSAGE RECEIVED IN FLIGHT. FLIGHT DIVERTED TO MKE. CREW COMPLIED WITH QRH. MESSAGE PERSISTED FOR ABOUT TWO MINUTES. LAV WAS UNOCCUPIED. PER MX CONTROL REMOVED AND REPLACED LAV SMOKE DETECTOR PER AMM 26-16. OPS CK GOOD.