As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: BITE TEST OF EMERGENCY POWER SUPPLY UNIT EMERGENCY LIGHT FAILED ON MESSAGE BATTERY FAULT ON 15 WL. MAINTENANCE REPLACED BATTERY AT 15WL AND PERFORMED SATISFACTORY OPERATIONAL CHECK AND BITE TEST PER AMM 33-50-00.