Interleaved boost converters with coupled inductors are a suitable fault-tolerant topology for fuel cell electric vehicles (FCEVs). However, the reliability of these converters has been a major concern, and the fault diagnosis control remains a challenge due to phase coupling. In this paper, a simple signal-based diagnostic method is proposed. It is mainly based on the average of the inductor currents to detect and identify the switch open-circuit fault. The proposed method is implemented on Matlab / Simulink and validated on Typhoon Hardware-in-the-loop (HIL) in closed-loop. The fault could be detected in less than two switching periods. A post-fault reconfiguration is applied to maintain optimal operation of the healthy phases. This fault-tolerant control is easy to implement and demonstrates great robustness in the case of load variations.