As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE NR 1 ENGINE EGT EXCEDANCE AND CONTINUED TO SURGE UNTIL ENGINE NEAR IDLE/LOW. DURING CREW DEBRIEF, OTHER ENGINE PARAMETERS NORMAL, ONLY EGT INDICATION WAS ERRATIC. EEC BITE SHOWED FAULT MESSAGES 77-28861 S3 PROBE OUT OF RANGE & 77-20871 S4 PROBE OUT OF RANGE. ACP EEC BITE & FOUND FOUR FAULTS SPECIFIC TO T495S3 & T495S4 EGT SIGNALS OUT OF RANGE. REF FIM 77-21 TASK 803 AND 804, T495 CONTROL TEMPS S4 APPEARS TO NOTED NO ERRATIC EGT INDICTIONS. ALL 4 PROBE SENSORS CHECKED GOOD. EEC BITE AFTER RUN SHOWS NO FAULTS. AIRCRAFT OK FOR SERVICE.