What was found
THREE HOURS INTO FLIGHT AT FL370, NR 1 AMBER COWL ANTI-ICE ILLUMINATED WITH ASSOCIATED "MASTER CAUTION" LIGHTS. THE LIGHT REMAINED ON STEADY OR INTERMITTENT DURING AND AFTER ACCOMPLISHMENT OF QRH PROCEDURE. ACFT GROUNDED. ACCOMPLISHED FIM TASK 30-21/801. FOUND NR 1 ENGINE CTAI DUCT OVERPRESSURE FAULTY. REMOVED NR 1 ENGINE TAI PRESSURE SENSOR IAW AMM 30-21-21-000-802. INSTALLED NR 1 ENG TAI PRESSURE SENSOR IAW AMM 30-21-21-400-801.