What was found
(CAN) ACFT WAS STARTED FOR A COMPANY FLIGHT. DURING RUN UP CHECKS, THE EOS, ELECTRONIC OVERSPEED SENSOR, CHECK WAS COMPLETED SATISFACTORILY. HOWEVER, UPON RETURNING THE EOS SWITCH TO THE OFF, NORMAL, POSITION, THE ENGINE AND NR SPEEDS RAPIDLY SURGED TO APPROXIMATELY 430 RPM WITH NO RESPONSE FROM THROTTLE LEVER CHANGES. ENGINE WAS SHUTDOWN. TROUBLESHOOTING REVEALED A FAULTY FCU.