As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING GROUND RUN, WITH NR 1 ENGINE RUNNING AT GROUND IDLE (70 PERCENT NR1) AND ROTOR BRAKE ENGAGED, THE ENGINE SHUT ITSELF OFF AFTER RUNNING ABOUT 3-5 MINUTES. THE MECHANIC REMOVED AND REPLACED THE MAG OVERSPEED SENSOR AND THE AIRCRAFT RETURNED TO SERVICE.