As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING OPERATIONAL TEST OF EMERGENCY LIGHTING SYSTEM MAINTENANCE FOUND EMERGENCY POWER SUPPLY UNIT 13WL FAULT MESSAGE. MAINTENANCE REPLACED THE R4 DOOR SLIDE AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK OF THE EMERGENCY LIGHTING SYSTEM.