As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS IN BASE MAINTENANCE: INOP EPSU-EMERGENCY POWER SUPPLY UNIT 12WL IN PASSENGER CABIN. REPLACED EPSU-EMERGENCY POWER SUPPLY UNIT 12WL IN PASSENGER CABIN I.A.W AMM33-51-38-000-001-A AND AMM 33-51-38-400-001-APERFORMED OPERATIONAL CHECK OF THE EPSU THRU BITE CHECK IAW AMMROTABLE PARTS CHANGE WAS INDICATED - 458723733-51-00-710-001-A CHECK OK AND PERFORMED THE INTERFACE AND POWER UP TEST OFTHE CIDS IAW AMM 23-73-00-740-005-A, TEST OK. REFER TO INDIVIDUAL SIGN OFF ENTRIES FOR WORK STEPS PERFORMED.