As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: ECAM HYDRAULIC YELLOW ENGINE 2 PUMP LOW PRESSURE ON CLIMB OUT. CREW TURNED ENGINE 2 PUMP OFF PER ECAM ACTION. AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO ORD WHERE IT LANDED SAFELY WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED ENGINE PUMP PRESSURE SWITCH PER AMM 29-13-17 AND ACCOMPLISHED A SATISFACTORY LEAK / OPERATIONAL CHECK.