As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE TO ATL, YELLOW HYD SYSTEM HI TEMP LIGHT ILLUMINATED. FOLLOWED QRH AND RETURNED TO MEM. MAINTENANCE REMOVED & REPLACED NR 2 ISOLATION VALVE P/N HTE9531-3 IAW RJ MM CH 29-10-14 201. RAN A/C ON GROUND 30 MINUTES, ACTUATING ALL HYDRAULICALLY ACTUATED COMPONENTS EXCEPT LANDING GEAR, NO HI TEMP ILLUMINATION NOTED. LEAK CKS ARE GOOD. A/C OK FOR SERVICE.