As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED INTO ORD DUE TO THE FLIGHT CREW REPORTING A YELLOW HYDRAULIC SYSTEM RESERVOIR LOW LEVEL ECAM MESSAGE DURING FLIGHT. AIRCRAFT LANDED SAFELY AT ORD WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND THE PTU MANIFOLD QUICK DISCONNECT FITTING O-RING DAMAGED AND LEAKING HYDRAULIC FLUID. REPLACED O-RING AND ACCOMPLISHED A SATISFACTORY LEAK CHECK PER AMM 29-13-15.