The BSE Sensex today dipped below the 17,000 level, losing nearly 277 points, as the second quarter earnings posted by IT major TCS, amid a weak global trend. The Sensex, which had lost 57 points in the previous session, fell nearly 277 points to close at around 16,748.The broad-based National Stock Exchange Nifty lost nearly 81 points to 5,037.50 led by stocks of IT and realty sectors on all-round selling.