What was found
#1 ENGINE TREND DATA SHOWS A SUDDEN SHIFT IN EGT HOT DAY MARGIN PREVIOUS MAINT CJ9 HARNESS AND S1 PROBE REPLACED. GROUNDED - YES. REMOVED AND REPLACED #1 J9 HARNESS REF AMM 73-21-06-400-803-F00, OPS NML REF AMM 73-21-00-700-802-F00. ACCOMPLISHED THE FOLLOWING TEST: EEC TEST, PASSED, NO FAULTS LOGGED. ACTUATOR TEST, TEST PASSED. EEC DISCRETES TEST, ALL PASSED REF PER SAME. TEMP MONITORING AFTER HARNESS CHANGE: S1- 23.37 S2- 20.50 S3- 20.64 S4- 27.71. GROUND VERTIFICATION SUCCESSFUL.