What was found
DURING DESCENT AT 33,000 FEET, NR 2 ENGINE OVERSPEED OCCURRED. AUTO THROTTLE WAS DISENGAGED, POWER LEVER WAS PULLED BACK, AND ENGINE RPM CONTINUED TO ACCELERATE. ENGINE WAS MANUALLY SHUTDOWN. AIRCRAFT DIVERTED TO PHL AND LANDED WITHOUT FURTHER INCIDENT. MAINTENANCE BORESCOPE AND ENGINE OVERSPEED INSPECTION REVEALED NO DISCREPANCIES. REPLACED THE NR 2 ENGINE CONTROL UNIT, OPERATIONAL CHECK OK.