The current trend of using object based design for real time control systems has the implication that traditional state based fault detection and recovery methods cannot be used directly. This problem is even more difficult for domain independent fault detection and recovery since most such methods are based on a formal analysis of the global state set. The paper presents a domain independent fault isolation, detection and recovery method for object based control systems based on constraints of the object architecture. Variations of the control behavior from normal cases are detected using a fuzzy state machine approach