As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MKE/PHL - FLT 5809 - EN ROUTE TO PHL, CREW RECEIVED A LOW OIL PRESSURE EICAS MESSAGE ON THE LEFT ENGINE. CREW DECLARED AN EMERGENCY AND SHUT DOWN THE LEFT ENGINE. AIRCRAFT LANDED IN PHL WITHOUT FURTHER INCIDENT. MAINTENANCE REMOVED AND REPLACED THE O-RINGS ON THE HYDRAULIC PUMP, LEAK CHECK GOOD. AIRCRAFT WAS RETURNED TO SERVICE. REF: OPER CONTROL NR MASA98194.