What was found
WHEN ACFT POWERED UP DURING SERVICING A FLASHING AMBER GOV LIGHT DISPLAYED ON ANNUNCIATOR PANEL. FAILURE CODE 123 CHECKED INDICATING "T4 FADEC L", GOING FURTHER INTO FADEC DATA -FAIL 1 CODE WAS 0020 (RAW T4.5 FAILURE) WAS DISPLAYED AND T4 INDICATION IN FADEC DATA WAS SOLID YELLOW WITH NO TEMP INDICATION NUMBERS. CONFIRMATION BOX, BOTH PYROMETRIC HARNESSES (LT AND RT) AND APPLICABLE ENG HARNESSES TESTED IAW MM, ALL SATISFACTORY. FINALLY REPLACED LT PYROMETRIC HARNESS WITH SERVICEABLE UNIT AND FLASHING AMBER GOV LIGHT DISAPPEARED. ACFT GROUND RUN, ALL SATISFACTORY. PYROMETRIC HARNESS SENT BACK.