As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APPROXIMATELY 20 MINUTES AFTER TAKE OFF, LAVATORY SMOKE DETECTOR FAULTED. CIDS PANEL SHOWED 2 RED LIGHTS. NO RESET WAS ATTEMPTED. REMOVED AND REPLACED THE LAVATORY AIR EXTRACT FILTERS IAW AMM 21-23-00. OK FOR SERVICE. THE AIRCRAFT WAS GROUNDED.