As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BOS - FLT 4852 - WHILE AT CRUISE, THE LEFT PGB OIL TEMPERATURE WAS READING LOW (40 DEGREE CELSIUS). AIRCRAFT DIVERTED TO BOS AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE LEFT THERMAL BYPASS VALVE. ENGINE RAN WITH ALL INDICATIONS READING NORMAL. (M)