As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRESSURIZATION WAS WORKING IN MANUAL MODE AT FL230. AUTOMATIC MODE WAS DEFERRED. DURING CRUISE THE CABIN CLIMBED INSTANTLY TOWARD CRUISE ALTITUDE AND WAS THERE WITHIN 10 SECONDS. THE MASKS DROPPED. INITIATED EMERGENCY DESCENT AFTER ATC CLEARANCE 5 MINUTES LATER. INSTALLED PNEUMATIC OUTFLOW VALVE IAW 21-30-00. INSTALLED ELECTRO-PNEUMATIC VALVE IAW 21-30-00. PRESSURIZED AIRCRAFT, ALL CHECKS OK AT THIS TIME.