As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: WHILE PERFORMING OPERATIONAL TEST OF THE EMERGENCY LIGHTS, MAINTENANCE FOUND CLASS 1 CODE ON MCDU SYSTEM REPORT PAGE. CODE STATES BAT/EPSU (11WL) EXT L. MAINTENANCE REPLACED THE BATTERY FOR EMERGENCY POWER SUPPLY UNIT 11WL AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK PER AMM 33-51-38