As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS DURING TAXI FOR TAKE OFF #3 FLIGHT ATTENDANT REPORTED A STRONG PLASTIC BURNING SMELL FROM LEFT AFT LAVATORY. THE FLIGHT ATTENDANT WAS NAUSEATED BY THE TIME WE RETURNED TO THE GATE. MAINTENANCE PERFORMED JOB CARD 05-96-70, SMOKE, ODOR FUMES INITIAL TROUBLESHOOTING. FOUND LAV SMOKE DETECTOR INOP WITH SLIGHT ODOR. REMOVED & REPLACED AFT LEFT LAV SMOKE DETECTOR IAW AMM 26-14-01. OPS CHECKS GOOD.