What was found
(CAN) DURING LEVEL FLIGHT FL. 250, ENGINE NR 2 PROPELLER SPEED WENT TO 1051 RPM, FOLLOWED BY POWERPLANT ON ED. THIS CASE WAS TREATED AS AN OVERSPEED AND QRH CONSULTED, ENDING UP WITH ENGINE SHUTDOWN, ON NR 2 ENGINE. EMERGENCY DECLEARED AND A NORMAL DESCENT TOWARDS BASE WAS INITIATED. LANDING PERFORMED AND TAXI TO REMOTE GATE WAS DONE. MAINTENANCE ARRIVED AND FOUND FAULT CODE 160 CH A AND B. FIM TASK 61-20-04-810-813 PERFORMED. NO CONTACT WITH MPU AND BUSS BARS. REMOVE AND REPLACED MPU. (TC NR 20070402001)