As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(LOG 6403814) AT FLIGHT LEVEL 310 SMELLED AN ABNORMAL SMELL ASSOCIATED WITH A WHINE. DONNED MASKS, SMELL WENT AWAY. SMOKE/ODOR EVENTS, NO EXTERNAL FLUID LEAKS, NO SYSTEMS OVERSERVICED. APU AND PACK COMPARTMENTS CLEAN AND NO CONTAMINATION. BOTH PACKS OPERATED WITH APU AND BOTH ENGINES AFTER LEFT ACM REPLACEMENT. REF LP 6403815.