As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DIRTY SOCKS SMELL ON FLIGHT DECK ON DESCENT PASSING THROUGH 5,000; APU WAS " OFF" NOT SMELLED IN AFT CABIN, SO SUSPECT LEFT ENGINE OR PACK ISSUE LASTED 1-2 MINUTES AND NO CREW ACTION WAS WARRANTED, NOR TAKEN, AS ODOR WAS FLEETING. MAINTENANCE FOUND LEFT OZONE FILTER CONTAMINATED AND REPLACED IT PER AMM 21-51-41. A SATISFACTORY OPERATIONAL / LEAK CHECK WAS ACCOMPLISHED WITH NO ODORS NOTED.