As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) AIRCRAFT RETURNED DUE TO PRESSSURIZATION FAULT. CABIN CONTINUED TO CLIMB PAST 11,000 FEET, OXYGEN MASKS DEPLOYED. LEFT PACK WATER SEPARATOR TEMPERATURE CONTROL VALVE FOUND INOPERATIVE WHEN PACK IN OPERATION. VALVE REPLACED AND CHECKED SERVICEABLE.