As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON INITIAL CLIMB, THE ACFT WOULD NOT HOLD A DIFFERENTIAL PRESSURE GREATER THAN 3.0 PSI. THIS RESULTED IN A "CABIN ALT" WARNING ON CLIMB THROUGH 16,200 FT. ATTEMPTED TO TROUBLE SHOOT TO NO AVAIL. ACFT RETURNED TO DEPARTURE. PERFORMED OPS CHECK IAW MM 21-30-00, NO DEFECTS NOTED.