This paper introduces a fault detection and adaptive controller reconfiguration that can determine on-line stable and free offset errors performance, detect faults quickly, and reconfigure the controller accord-ingly using recursive autoregressive exogenous estimator (RARX). A fault detection and controller system consists of two main parts: the first is the fault detection and the second is the controller reconfiguration. For the first issue, we propose a simple scheme for de-tecting faults with RARX estimator. For the second issue, we consider and install a digital adaptive controller with pole replacement. Simulations for the sug-gested system are illustrated and analyzed. © Fuji Technology Press Ltd.