As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED; UPON TAKEOFF @700 FT , WARNING MESSAGE LAV SMOKE INDICATED AND PERSISTED FOR AT LEAST A MINUTE, UPON LEVELING OFF AND VECTORING BACK AROUND, MESSAGE DISAPPEARED ON THE DESCENT DOWN. CORR ACTION- MX PERFORMED INSPECTIONS AND TEST OF LAV SMOKE SYS IAW EMB AMM. NO FAULTS OR DEFECTS NOTED AT THIS TIME. NO VISUAL OR ODOR INDICATION OF SMOKE/FIRE IN LAVATORY.