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

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