What was found
(CAN) ON APPROACH, THE CREW NOTICED A PROGRESSIVE DROP IN NR 2 PROPELLER'S RPM. ATTEMPTS TO CONTROL PROP RPM BY SWITCHING EEC TO MANUAL WERE UNSUCCESSFUL. THE CREW ELECTED TO SHUT DOWN THE ENGINE, AND THE AIRCRAFT WAS DIVERTED. POST-FLIGHT INSPECTION FOUND THE PROPELLER CONTROL UNIT FAULTY. THE PROP CONTROL UNIT WAS REPLACED, CHECKED SERVICEABLE, AND THE AIRCRAFT RETURNED TO SERVICE.