As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 7939 - IAD - DURING DESCENT THE NR 2 ENGINE OIL PRESSURE DROPPED TO 15-20 PERCENT AND SHUT THE ENGINE DOWN. MAINTENANCE INSPECTED AND FOUND AN OIL LEAK BEHIND NR 2 GEN AT MAGNETIC/MECHANICAL CARBON SEAL. REMOVED AND REPLACED THE CARBON SEAL FOLLOWED BY A LEAK CHECK OF THE NR 2 ENGINE WITH NO DEFECTS/LEAKS NOTED.