As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: FAULT MESSAGE ESCAPE SLIDE LT/EPSU (13WL) AFT L FAULT, ON EPSU 13WL FAULT RED LIGHT COME ON EXTERIOR LIGHTS FAULT DURING SYSTEM TEST. MAINTENANCE REPLACED THE L4 DOOR SLIDE AND ACCOMPLISHED A SATISFACTORY OPERATIONAL CHECK OF THE EMERGENCY LIGHTING SYSTEM WITH NO FAULTS NOTED.