This note presents a control scheme for fault diagnosis and tolerance in asynchronous sequential machines. The considered asynchronous machine is subject to permanent faults, so the system remains in the faulty condition indefinitely after the occurrence of fault inputs. When the machine has a certain structural redundancy, we can design a corrective controller and observer that diagnose faults and compensate the closed-loop system so that it can maintain the normal input/output behavior. The proposed framework is based on the output feedback control scheme and asynchronous techniques.