As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON REACHING AN ALTITUDE OF 30,000', PAX DOOR OPEN CAS WARNING MESSAGE ILLUMINATED. DECLARED AN EMERGENCY, STARTED AN EMERGENCY DESCENT AND RAN THE CHECKLIST IN THE QRH. RETURNED TO DEPARTURE AND LANDED WITHOUT INCIDENT. MAINTENANCE OPERATED THE DOOR SEVERAL TIMES AND COULD NOT DUPLICATE THE DISCREPANCY.