Abstract: Compared with the single inverter drive, the dual-inverter open-end winding configuration especially that with common mode connected DC buses proposed recently, is a more ideal drive topology for new energy vehicles, particularly those powered with multi-sources, considering its merits of not only better operation performance, but also greater capability in switch fault tolerance. It is also the capability of fault tolerance, however, that results in difficulty in fault diagnosis. Referring to this open-end winding drive with common mode connected DC buses, the control scheme emphasizing on the zero-sequence control as well as the neutral point voltage control were designed in this paper, based on which a single-switch open circuit fault diagnosis technique was proposed by analyzing the features of the stator current in the presented unipolar operation mode. In this technique, both the faulty phase and the faulty switch pair were found out firstly through calculating the stator phase currents’ average values. Following that, to localize the specific faulty switch in the faulty switch pair, the bridge of the faulty phase was forced into a unipolar operation mode, in which different features can be identified to the two switches in the same faulty switch pair, allowing the specific faulty switch localized. At last, the validity of the proposed diagnosis technique was confirmed through experiments on a laboratory test rig.