As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 748 EN-ROUTE, LOST ENG 1 HYD B SYS PRESS AT FL 370. FLIGHT DIVERTED & LANDED WITHOUT FURTHER INCIDENT. PERFORMED BLEEDING OF THE BLUE HYD SYS IAW TASK 29-00-00-870-805-A. REPLACED BLUE RESERVOIR AIR PRESS SWITCH IAW TASK 29-31-11-000-802-A.