As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
IAH - FLIGHT 2172 - THE CREW REPORTED, RECEIVED A PACK ONE VALVE CLOSED MESSAGE ON EICAS. THE AIRCRAFT RETURNED TO IAH WHERE IT LANDED WITHOUT INCIDENT. MAINTENANCE REMOVED AND REPLACED THE NUMBER ONE PACK DUCT TEMPERATURE SENSOR, OPERATIONALLY TESTED WITH NO DEFECTS, AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.