As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AIRCRAFT RETURNED TO ORD ON ACCOUNT OF PRESSURIZATION PROBLEM. AN EMERGENCY WAS DECLARED. MAINTENANCE REMOVED AND REPLACED THE #2 ENGINE OVER PRESSURE VALVE IAW AMM 36-11-53. OPS CHECK GOOD. MAINTENANCE ALSO FOUND #2 ENGINE ANTI-ICING DUCT LEAKING AND FOUND A WIRE BUNDLE @ 12:00 POSITION ADJACENT TO FWD THRUST REVERSER GUIDE ROD CHAFFING.