As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON FLIGHT 3919 DURING CRUISE THE CREW REPORTED, RECEIVED AN EICAS MESSAGE: HYDRAULIC 2 LOW QUANTITY FOLLOWED BY HYDRAULIC SYSTEM 2 FAIL MESSAGE. THE CREW DECLARED AN EMERGENCY AND DIVERTED TO STL. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE NUMBER 2 ENGINE DRIVEN HYDRAULIC PUMP. THE OPERATIONAL CHECK WAS GOOD IAW EMB AMM 29-10-03. THE AIRCRAFT WAS RETURNED TO SERVICE.