What was found
NR 1 ENGINE EXPERIENCED AN INCREASE IN DELTA EGT AND A DECREASE IN EGT HOT DAY MARGIN. FUEL FLOW AND CORE SPEED REMAINED STABLE. ACFT GROUNDED. ON THE NR 1 ENGINE, PERFORMED FIM 77-05, TASK 801, FOUND FAULT CODE 77-20861 ON MULTIPLE FLIGHT LEGS IN FAULT HISTORY. PERFORMED FIM 77-21, TASK 803, DURING T49.5 PROBE AND EGT SYSTEM INSPECTION, FOUND T49.5 PROBES S2 AND S3 OUT OF RESISTANCE LIMITS IAW AMM 77-21-01-200-801-F00. REMOVED AND REPLACED THE S2 AND S3 T49.5 PROBES IAW AMM 77-21-01/401. OPS CHECKED SATISFACTORY. PERFORMED SUCCESSFUL REPAIR CONFIRMATION OF FIM 77-05, TASK 801, AND FIM 77-21, TASKS 801-804.