As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING AIRCRAFT CLIMB, THE EMERGENCY PRESSURIZATION VALVE OPENED ALLOWING UNCONDITIONAL BLEED AIR INTO THE CABIN. CABIN TEMPERATURE INCREASED AT AN UNCONTROLED RATE. AIRCRAFT RETURNED TO THE AIRPORT FROM WHICH IT DEPARTED. THE EMERGENCY PRESSURIZATION VALVE WAS REPLACED. AIRCRAFT GROUND RUN "S".