Multichip insulated gate bipolar transistor(IGBT) modules are widely used in high-power converters, where condition monitoring plays a crucial role in improving the reliability of power equipment. This paper proposes a fault detection method for identifying partial chip failures in multichip IGBT modules by analyzing variations in turn-on delay time. First, the influence of chip failure on the turn-on process is analyzed, establishing the relationship between chip failure and turn-on delay. Based on this relationship, a fault monitoring method is developed to correlate turn-on delay with the number of failed chips. The effectiveness of the proposed method is verified by experimental testing. The results show that this method is significant for improving the operational reliability of power converters.