As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: FAULT MESSAGE FOR EPSU COM AFT L DISPLAYED DURING EMERGENCY POWER SUPPLY UNITS BY BITE-CHECK - MAINTENANCE REPLACED THE BATTERY FOR EMERGENCY POWER SUPPLY UNIT 13WL AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38