Abstract: This paper takes the 2020 BYD Qin EV as the research object, systematically analyzes the structural composition, control logic and workflow of the keyless entry system, and constructs a complete methodology for fault diagnosis and maintenance. Based on the BYD vehicle network architecture, the working principle of the keyless entry system is elaborated in detail, covering the 125 kHz low-frequency wake-up signal transmission, 315 MHz high-frequency radio frequency communication, the authentication process between the body control module (BCM) and the smart key, as well as the control logic of actuators such as door locks and trunk locks. The study shows that the system adopts a hierarchical control strategy, realizes data interaction between modules through CAN/LIN bus, and is equipped with a dynamic encryption authentication mechanism to ensure security. Aiming at typical faults of the keyless entry system, the paper proposes a three-stage diagnostic method of "signal traceability, segmental troubleshooting, and data verification", providing references for the fault diagnosis of anti-theft systems in new energy vehicles.

Key words: BYD Qin EV; keyless entry; hierarchical control; the three-stage diagnostic method

摘要： 文章以 2020 款比亚迪秦 EV 为研究对象，系统剖析无钥匙进入系统的结构组成、控制 逻辑及工作流程，构建了一套完整的故障诊断与检修方法论。基于比亚迪整车网络架构，详 细阐述无钥匙进入系统的工作原理，涵盖 125 kHz 低频唤醒信号传输、315 MHz 高频射频通 信、车身控制模块（BCM）与智能钥匙的认证流程，以及门锁、尾箱锁等执行机构的控制逻 辑。研究表明，该系统采用分层式控制策略，通过 CAN/LIN 总线实现各模块间的数据交互， 并具备动态加密认证机制，确保安全性。针对无钥匙进入系统的典型故障，文章提出“信号 溯源、分段排查、数据验证”的三段式诊断方法，为新能源汽车的防盗系统的故障诊断提供 一些参考。

关键词: 比亚迪秦 EV；无钥匙进入；分层式控制；三段式诊断方法