As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED A LAVATORY SMOKE WARNING INDICATION ON EICAS WITH NO INDICATION OF SMOKE OR FIRE. MAINTENANCE INSPECTED LAVATORY FOR SMOKE AND EVIDENCE OF FIRE WITH NOTHING FOUND. MAINTENANCE ALSO PERFORMED OPS CHECK OF LAVATORY SMOKE DETECTOR SYS GOOD. ACFT WAS APPROVED FOR RETURN TO SERVICE.