As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW NOTICED BURNING SMELL STRONG MID CABIN TO AFT CABIN, SMELL DIMINISHED AFTER RIGHT PACK TURNED OFF. FOUND SOURCE OF ODOR TO BE FROM PACK 2. REMOVED AND REPLACED AIR CYCLE MACHINE (ACM) IAW AMM 21-52-21. ALSO REPLACED RECIRCULATION FILTERS AND CLEANED BLEED AIR PLUMBINGS. NO MORE BURNING SMELL NOTED.