What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS AT FL270 GOT IAS DISAGREE ON CAPT. FLIGHT DISPLAY. DISCONNECT AUTO PILOT, STABILIZED AIRPLANE. ENG. ANTI ICE WAS ON, TEMP PLUS 7 CELSIUS. ON DESCENT CHECKLIST, RECALL SHOWED ENG. LIGHT. ACCOMPLISHED QRH PROCEDURE FOR AIRSPEED UNRELIABLE. F.O. LANDED AIRCRAFT. EMERGENCY DECLARED. NO APPARENT DAMAGE NOTED BY ARFF. PROBE HEAT WAS ON SINCE THE BEFORE START CHECKLIST. MAINTENANCE ACCOMPLISHED FIM 31-62-00-810-876 AIRSPEED DISAGREE TASK . FOUND LEFT PITOT PROBE RESISTANCE VALUES OUT OF LIMITS. REPLACED CAPT. PITOT PROBE AND ACCOMPLISHED INSTALLATION TEST IAW AMM 34-11-01-000-801. PERFORMED LEFT PITOT SYSTEM LEAK TEST IAW AMM 34-11-00-790-810. NO LEAK NOTED. OK FOR SERVICE.