As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW REPORTED A LAVATORY SMOKE DETECTOR EICAS MESSAGE WHILE AT THE GATE WITH NO VISIBLE SMOKE. MX INSOPECTED THE ACFT AND R & R THE LAVATORY SMOKE DETECTOR, OPS TESTED WITH NO DEFECTS, AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE.