Abstract: ［Objective］ As a replacement for relays, LCUs (logic control unit) are widely used in urban rail transit trains in China, participating in vehicle control alongside train networks and hardwired signals. Analyzing typical faults encountered during LCU operation and exploring reliable solutions are crucial for ensuring the safety and reliability of metro trains. ［Method］ Focusing on typical LCU faults observed since the opening of Ningbo Rail Transit Line 3 and Line 4, and based on the collected key data, the output waveforms at critical points of the faulty boards are monitored and analyzed to investigate fault mechanisms. The identified causes include component failures on input/output boards and failures in activating the redundancy switching mechanism. Optimization proposals are formulated to enhance fault detection and redundancy switching mechanisms, and output circuit parameters of the driver chips are adjusted. Finally the effectiveness of the optimization proposal is validated through simulation experiments and onboard testing. ［Result & Conclusion］ The dual machine hot-standby redundancy and fault condition active switching mechanisms of LCUs are key advantages over conventional relays and play a critical role in ensuring stable train operation. Testing under normal and voltage regulator fault conditions confirms that the optimization proposel can effectively improve the availability of LCUs.