As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH- DURING PREFLIGHT THE CREW NOTED THAT THE EMERGENCY LIGHTS FAILED TO ILLUMINATE. IAH- MAINTENANCE REMOVED AND REPLACED THE NR 4 EMERGENCY BATTERY PACK, PERFORMED A OPERATIONAL CHECK OF THE EMERGENCY LIGHTING SYSTEM, NO DEFECTS NOTED AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.