What was found
FIRE/OVERHEAT SYSTEM ADVISORY MESSAGE IN FLIGHT. RAN QRH MESSAGE CLEARED THEN RE APPEARED. T/S PER FIM 26-11 FT 804, WDM 26-11-11 & AMM 26-11-00. FOUND DUCT NOT SEATED PROPERLY, RESECURED. RAN ENGINE, REF 71-00-00 TO 35% N1 FOR 20 MIN, NO FAULTS NOTED.