As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ACCOMPLISHING T/C 78273000, FOUND THE NR 1 ENGINE ECONOMIC FAULT CODE 77-20871, TOP LEFT EGT SIGNAL T495S4 IS OUT OF RANGE. ACFT GROUNDED. EVALUATION INPUT MONITORING OF T49.5 SYSTEM FOR PROBE S4 SHOWS BLANK WITH NO DISPLAY VALUE. PERFORMED 77-21 / 804. ACCOMPLISHED EGT CLEANING IAW AMM 77-21-00-140-801. TEMP PROBE COMPARATIVE VALUES WITHIN 25 DEGREES. PERFORMED EEC TEST IAW AMM 73-21-00-700-804-F00. TEST PASSED WITH NO EEC FAULTS.