What was found
ATB, TEMP ZONE L EICAS MESSAGE DISPLAYED DURING CRUISE. FOLLOWED QRH AND WAS UNABLE TO RESET SYSTEM. RESULTED IN ATB CMC MAINTENANCE MESSAGE 21098, FIM TASK 21-61-00-810-852, REV. 2025/07/15 ACCOMPLISHED, FLIGHT DECK DUCT TEMPERATURE SENSOR T1647 REPLACED, AMM REFERENCE: 21-61-16/401 CONFIG 1, REV NO. / DATE : 48 / 15 JUL 2025, TRIED TO REPLACE THE IASC #1 FOR PRECAUTIONARY REASON, BUT ALL ATTEMPTS OF SOFTWARE INSTALLATION VIA ANSP WHERE NOT WORKING, SYSTEM TESTS PERFORMED TEMPERATURE REGULATION AND DISPLAYED VALUES ARE FINE.