In this article, we investigate how to identify faulty sensors in piezoelectric actuators used for precise positioning. Four sensors are distributed along the actuator’s cantilever structure to measure the deflection (displacement) at various points. We suggest identifying the sensor and detecting the fault in one of the sensors, which is thought to be faulty or producing a degraded signal. To address this, we suggest using transmissibility operators, which are mathematical estimators that estimate sensor measurements based on another set of sensor measurements within the same system. This estimation is highly robust against any external excitations/disturbances, as well as any unknown nonlinearities or unmodeled dynamics. The estimation robustness allows failure detection to be carried out even in significant actuator hysteresis nonlinearity and outside disturbance. Simulation results with various sensor fault conditions verified the suggested strategy.