As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5641, IAH TO LBB. THE FLIGHT CREW RECEIVED A HYDRAULIC SYSTEM 2 LOW PRESSURE MESSAGE ON EICAS. THE SYSTEM 2 QUANTITY INDICATED 0% BUT THE PRESSURE REMAINED NORMAL DURING FLIGHT. THE AIRCRAFT DIVERTED TO AUS AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE HYDRAULIC SYSTEM AND FOUND NO LEAKS. THE SYSTEM 2 RESERVOIR WAS FOUND TO BE AT THE FULL LEVEL AND THE SYSTEM 2 QUANTITY INDICATION WAS PLACED ON MEL. LATER THAT DAY THE SYSTEM 2 RESERVOIR WAS REPLACED AND THE MEL WAS CLEARED WITH NO FURTHER DEFECTS NOTED.