As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE ACFT HAD THE AUTO PRESSURIZATION MODE DEFERRED WHEN IT DEPARTED. DURING CLIMB-OUT, WHILE CLIMBING THROUGH 9,000 FT THE CABIN ALTITUDE INDICATED 8,500 FT. THE CREW LEVELED OFF AT 10,000FT THEN DESCENDED TO 9,000FT. THE CREW WAS UNABLE TO PRESSURIZE THE CABIN PROPERLY IAW POH SO IT WAS DECIDED TO RETURN TO DEPARTURE WHERE THE ACFT LANDED WITHOUT INCIDENT. MX CLEARED THE FAULT AND MEL BY REPLACING THE DIGITAL PRESSURE CONTROLLER. THE PRESSURIZATION SYS OPS CHECKED NORMALLY.