What was found
PIT - FLT 991 - EN ROUTE FROM PHL TO DFW, SOUTH OF PIT, CREW REPORTED THE NR 2 ENGINE EGT SPIKED TO 1,000 DEGREES WITH THE RED OVERHEAT LIGHT ILLUMINATING. ALL OTHER ENGINE INDICATIONS WERE NORMAL. CREW REDUCED POWER ON THE NR 2 ENGINE AND THE LIGHT EXTINGUISHED. FLIGHT DIVERTED TO PIT AND LANDED WITHOUT FURTHER INCIDENT. AN EMERGENCY WAS DECLARED. MAINTENANCE REMOVD AND REPLACED THE NR 2 ENGINE EGT CORE HARNESS DUE TO MEGGER TEST IRREGULARITIES. RAN NR 2 ENGINE AT TAKEOFF POWER FOR SIX TO EIGHT MINUTES, THEN TAXIED AIRCRAFT AT HIGH POWER SETTING. ALL CHECKED NORMAL PER MM 77-21-00. (M)