As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED AND IS IN CHECK FOR SCHEDULED MX. DURING OPC FOUND EPSU BATTERY 14WL INOP, REPLACEMENT IS REQUIRED IAW AMM 33-51-00-810-869-A REV 105. CORRECTIVE ACTION: REPLACED EPSU BATTERY 14WL IAW AMM 33-38-400-002-A REV 105.