With ever growing concerns on energy crises and environmental issues Proton Exchange Membrane Fuel Cell is favored in automotive applications because it is clean efficient and low noise A fuel cell hybrid powertrain is composed of a fuel cell system as the primary power source a battery as the secondary power source and an electric motor In order to improve the reliability a distributed control system that can be preserved even under faulty cases is necessary This paper presents an active fault tolerance control system (AFTCS) for a fuel cell/battery hybrid powertrain applied to a city bus The AFTCS consists of a system for fault detection and diagnose and a reconfigurable controller Algorithms to detect and isolated three kinds of important faults are introduced The real time applicable reconfigurable controller is exploited to recover the pre fault system performance as much as possible Experimental results show the effectiveness of the proposed system (C) 2010 Professor T Nejat Veziroglu Published by Elsevier Ltd All rights reserved