As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING PUSH BACK, AND ENGINE START, THE LAVATOPRY SMOKE DETECTOR STARTED GOING OFF. THE LED SHOWED RED AS ALARM SOUNDED. ALARM STOPPED AFTER ABOUT THREE MINUTES & LED LIGHT WAS GREEN. NO EVIDENCE OF SMOKE BUT LAVATORY HAD A FOUL ODOR. REMOVED AND REPLACED LAVATORY SMOKE DETECTOR IAW MM 26-13-01-4. PERFORMED ADJUSTMENT TEST IAW MM 26-13-00-5, AND 26-13-00-755-016. OPS CHECKED GOOD. ACFT OK FOR SERVICE.