What was found
(CAN) TROUBLE SHOOTING WAS PERFORMED AND THE MAINTENANCE DIAGNOSTIC COMPUTER (MDC) SHOWS FOLLOWING MESSAGES `TDR 1 OFF/NO OUTPUT` AND `RTU 2 FAILED/WIRING NO OUTPUT/NO BUS TO IOC`. RTU NO. 2 WAS IDENTIFIED AS SOURCE F THESE MESSAGES. ALSO TCAS AND XPONDER 2 ARE WORKING NORMALLY, WHEN RTU 2 INHIBIT PUSH BUTTON IS PUSHED. RTU NO. 2 REPLACED AND SYSTEM TESTED ACC. AMM TASK 23-81-01-000/400-801 REV.60. AFTER PART REPLACEMENT AND SUCCESSFULLY TESTING THE AIRCRAFT WAS HANDED OVER TO FLIGHT OPS. (TC# 20190408015)