As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED. MUSTY, FOUL ODOR DURING DESCENT AROUND 5,000' TO AFTER LANDING.IN COCKPIT THE ODOR CAME FROM 4 EYEBALL AIR VENTS. REPLACED APU AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK WITH NO ODORS NOTED, PER TASK CARDS 26L31049003 AND 26C31046016.