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 DURING DEPARTURE WITH ASSOCIATED ELECTRICAL ODOR. WENT AWAY AFTER A FEW MINUTES BUT THEN RETURNED FAINTLY AND INTERMITTENLY UNTIL ON THE GROUND. AIRCRAFT MADE AN UNEVENTFUL AIR TURN BACK. MX PERFORMED FAULT ISOLATION IAW FIM 21-20-00-801A & 803A WITH NO FAULTS NOTED. NO LAVATORY SMOKE WARNING INDICATED. NO ABNORMAL ODORS NOTED. ACFT WAS APPROVED FOR RETURN TO SERVICE.