What was found
DURING OUR DESCENT, AT ABOUT FL 330, RECEIVED AN AMBER CAS "LT ENGINE VIBRATION" MESSAGE. FOLLOWED CHECK LIST. AFTER A MIN THE CASE MESSAGE WENT OUT AND CAME BACK ON SEVERAL TIMES AND RECEIVED THE RED MASTER WARNING LIGHT "LT ENGINE VIBRATION". AGAIN, FOLLOWED THE CHECK LIST. AS A PRECAUTION SHUT THE LT ENGINE DOWN. BORESCOPED LT ENGINE, NO DEFECTS NOTED. TOOK FUEL SOAP SAMPLE AS WELL IAW MFG REP. REPLACED ENGINE VIBE MONITORING UNIT IAW MM 77-41-10 AND ENG ACCELEROMETER IAW 77-30-00, OPS CHECK GOOD.