As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OMA - FLIGHT 4435, RECEIVED A LAV SMOKE/FIRE WARNING MESSAGE. NO FIRE NOTED AND NO SMELL NOTED. MAINTENANCE PERFORMED A OPERATIONAL CHECK WITH NO DEFECTS, NO SMELL NOTED. PLACED SMOKE DETECTOR ON MEL. REPLACED SMOKE DETECTOR. AIRCRAFT RETURNED TO SERVICE.