What was found
ON FLIGHT 2915 ON DESCENT THE CREW REPORTED, RECEIVED AN AIR/ GROUND FAIL MESSAGE ON ECIAS FOR A FEW SECONDS AFTER GEAR EXTENSION AND THEN CLEARED. A CORRESPONDING THRUST INCREASE WAS NOTED WITH AIR / GROUND AND THE ECIAS MESSAGE DID NOT APPEAR TO GO AWAY. THE CREW PERFORMED THE CHECKLIST FOR AIR / GROUND FAIL MESSAGES AND DECLARED AN EMERGENCY. THE AIRCRAFT LANDED WITHOUT INCIDENT. THE AIRCRAFT WAS REMOVED FROM SERVICE. TROUBLESHOT IAW EMB FIM 32-63-00 NO CENTRAL MAINTENANCE COMPUTER MESSAGE FOUND, THE NOSE LANDING GEAR PROXIMITY SWITCH WAS VERY DIRTY. CLEAND AND PERFORMED OPERATIONAL CHECK IAW AMM 32-60-00. NO PARTS REMOVED OR REPLACED. THE AIRCRAFT WAS RETURNED TO SERVICE.