As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: WHEN PERFORMING EMERGENCY LIGHT TEST PER PS CHECK- CIDS 1 EPSU SYST TEST BAT/EPSU (11WL) EMER L FAULT IS DISPLAYED. REPLACED EMERGENCY POWER SUPPLY INIT 11WL(AALA202108278020) AND BATTERY PACK (AALA202108271828) PER AMM 33-51-38. A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED.