As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
A/C DECLARED EMERGENCY LANDING DUE TO A PRESSURIZATION PROBLEM.. PILOT NOTED POSSIBLE PRESSURIZATION ISSUE. CABIN ALT LESS THAN ZERO ON OVERHEAD WITH DIFFERNTIAL ABOVE 6. PRESSURIZATION SCHEDULE IS NORMAL FOR FLIGHTS WITH ALTITUDE UNDER 18,500FT PER SDS 21-30-00-003.