What was found
(CAN) UNCOMMANDED IN-FLIGHT SHUTDOWN OF NR 4 ENG. DURING FINAL APPROACH. CONNECTOR IDENT (P52) ON BACK-UP OVERSPEED CONTROLLER FOUND TO BE SHORTED INTERNALLY. VOLTAGE LEAKING ACROSS VARIOUS PINS ON PLUG ALSO OUT TO OVERSPEED FUEL BYPASS/SHUT-OFF VALVE. THIS IS WHAT ACTIVATED FUEL BYPASS VALVE, CAUSING ENG TO SHUTDOWN. REPLACING (P52) CONNECTOR (P/N MS3476W14-19S) WILL ALSO REPLACE SECONDARY/BACK-UP CONTROLLER AS PRECAUTIONARY MEASURE (TO HAVE IT BENCH CHECKED TO ENSURE THERE WAS NO INTERNAL DAMAGE CAUSED BY STRAY VOLTAGE). ONCE SYS IS RE-ASSEMBLED, WILL CARRY OUT FURTHER CHECKS TESTING. GROUND RUNS, CARRIED OUT FUNCTIONING OVERSPEED ON PARTICULAR ENG WITH NO FAULTS AND SYS WAS GROUND CHECKED SERVICEABLE.