This paper develops conditions for sensor fault detection and isolation of nonlinear descriptor systems. The proposed methodology is based on a bank of observers, thus a novel approach is proposed to design Takagi-Sugeno observers in descriptor form. Traditionally, for descriptor systems, the designing conditions employ an augmented state vector whose elements are the state and its derivative. The proposed approach overcomes previous results in the literature by means of a novel augmented estimated vector, therefore conditions in terms linear matrix inequalities are directly obtained. The effectiveness of the given methodology is illustrated through a numerical example.