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: DID NOT PASS OPERATIONAL TEST OF EMERGENCY POWER SUPPLY UNITS BY BUILT IN TEST EQUIPMENT CHECK. PERFORMED FAULT CONFIRMATION AND FAULT ISOLATION PER TSM 33-51-00-810-822-A AND REPLACED POWER-EMERGENCY SUPPLY (10WL) PER AMM 33-51-38-400-001-A.