As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING TAXI AND DE-ICE, FLIGHT ATTENDANT HEARD A LOUD NOISE AND STRONG BURNING ORDER FROM AFT LAVATORY AIRCRAFT RETURNED TO GATE. NO LAVATORY WILL FLUSH. REMOVED AND REPLACED THE VACUUM GENERATOR PER THE AMM 38-31-64.