As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PHL - FL 3 - WITH LEFT PACK ON MEL, AIRCRAFT DEPARTED PHL FOR LAX. PASSING THROUGHT 10,000 FT THE CREW RECEIVED THE EICAS MESSAGE 'R ENG PRV' AND SECURED THE RIGHT BLEED SYSTEM. FLIGHT RETURNED TO PHL AND LANDED WITH NO FURTHER INCIDENT. MAINTENANCE REPLACED THE RIGHT OVERPRESSURE SWITCH FOR THE BLEED PROBLEM, AND THE LEFT FLOW CONTROL VALVE FOR THE LEFT AIR CONDITIONING PACK PROBLEM. (M)