As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW RETURNED TO DTW FOLLOWING FAILURE OF THE YELLOW HYDRAULIC SYSTEM. THE AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. REPLACED PTU FLOW CONTROL VALVE AND ASSOCIATED SEALS. REF AVRO AMM CH 29-20-24 PN AIR91762-1, SN ON LK8505340. SERVICED/BLED SYSTEM.