As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GE DIAGNOSTICS REPORTS AN INCREASE IN CRUISE EGT WITH A CORRESPONDING DECREASE IN EGT MARGIN ON NR 2 ENGINE ALL OTHER PARAMETERS NORMAL. FAULT CODE 77 20872 LOGGED IN NR 2 EEC FOUND S1&S4 VALUE DIFFER BY MORE THAN 200 DEG. REPLACED S4 TEMP PROBE REF MM 77 21 01. GROUND VERIFICATION TEST PASSED.