What was found
DIAGNOSTIC REPORTS NR 1 ENGINE TREND DATA SHOWS A SHIFT IN CRUISE AND TAKEOFF MARGIN INDICATIVE OF EGT INDICATION ERRORS. ACFT GROUNDED. WHILE COMPLYING WITH TC 78273000 FOUND ECONOMIC FAULT 77-20861 ON ENGINE 1ESN894921. READINGS OF ENGINE NR 1 T49.5 PROBES S1=69.27, S2=33.13, S3=357.45, & S4=87.47. ACCESSED ENG NR 1 T49.5 HARNESS AND ACCOMP. T49.5 PROBE AND EGT SYS INSP FOUND S3 RESISTANCE OUT OF LIMITS. REF MM 77-21-01-200-801. ACCOMPLISHED EGT CLEANING OF ALL EGT HARNESS CONNECTIONS. RECHECKED RESISTANCE OF S3 NOW WITH IN LIMITS. ACCOMPLISHED EEC TEST, TEST PASSES NO EEC FAULT. REF. MM 77-21-00-140-801.