As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) ON CLIMB AIRCRAFT FAILED TO PRESSURIZE. AIRCRAFT RETURNED TO BASE AND MAINTENANCE FOUND NOTHING CONCRETE FOR DEFECT. LINES DRAINED OF ANY MOISTURE AND REPLACED REGULATOR FOR SAFETY REASONS. GROUND RUNS CARRIED OUT AND AIRCRAFT RETURNED TO SERVICE (TC NR 20091211008)