As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: HYD Y RSVR LO LVL ECAM. FOLLOWED ECAM AND QRH PROCEDURES. DIVERTED TO STL, LANDED WITHOUT INCIDENT. MAINTENANCE UPON WALKAROUND INSPECTION DISCOVERED LEAKING HYDRAULIC FLUID FROM W/W. CHANGED HYDRAULIC FITTING AND ORING ON YELLOW SYSTEM PTU MANIFOLD LAW AMM 29-13-15.