As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL 310 RECEIVED LEVEL 3 "CABIN ALTITUDE" ALERT WITH NO OTHER NOISE OR INDICATIONS. ENG A/I WAS ON. FOLLOWED QRH AND COULD NOT (WITH 3 PACKS) MAINTAIN INDICATED CABIN ALTITUDE TO BELOW 10,000 FT. CABIN ALTITUDE INDICATED CLIMB WITH DDP AT APPROX 9.1. COULD NOT CONTROL CABIN ALT IN AUTO OR MANUAL. REMOVED AND REPLACED AFT UPPER POS PRESS RELIEF VALVE. VALVE OPS CK OK. REF MM 21-34-01-4. ALSO, REMOVED AND REPLACED CPAM. OPS CK STILL REQ REF MM 21-31-08-4.