As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: DURING PERIODIC SERVICE CHECK FOUND CLASS 1 FAULT CABIN INTERCOMMUNICATION DATA SYSTEM 1, EMERGENCY POWER SUPPLY UNIT SYSTEM TEST BATTERY EMERGENCY POWER SUPPLY UNIT (13WL) AFT LEFT, MESSAGE. REPLACED FAULTY EMERGENCY POWER SUPPLY UNIT BATTERY AT 13WL PER AMM 33-51-38.