As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: DURING CLIMB AND PASSING THROUGH 12K-13K FEET CABIN VERTICAL SPEED SPIKED TO 4000 FEET PER MINUTE FLIGHT CREW STOPPED THE CLIMB, DECLARED AN EMERGENCY AND RETURNED TO ORD WHERE IT LANDED SAFELY WITHOUT FURTHER INCIDENT NOTE: NO ECAM MESSAGES AND NO WARNINGS. REPLACED CABIN PRESSURE CONTROLLER PER AMM 21-31-34 (AALA202204042586) AND REPLACED OUTFLOW VALVE PER AMM 21-31-51. (AALA202204042840)