Abstract: This paper studies the keyless entry and start system of the Volkswagen Magotan B8L, discussing its architecture, functions and typical fault diagnosis methods. The KESSY system is mainly composed of multiple control modules such as J965, J519, J285, and antennas, and realizes communication among the modules through controller area network (CAN)/local interconnect network (LIN) buses. It relies on the anti-theft system to complete multi-layer dynamic encryption verification to achieve keyless door unlocking and engine starting. This paper combines specific cases to analyze the fault that the abnormal CAN bus voltage caused by the internal short circuit of the KESSY control module (J965) results in the inability to unlock the door and start the engine. The fault was located and repaired through methods such as voltage detection, module plugging and unplugging, and replacement. This case highlights the challenges posed by the modular, networked, and integrated characteristics of the KESSY system to the systematic thinking of maintenance personnel, providing theoretical basis and practical reference for automotive maintenance.

Key words: Magotan B8L; KESSY; collaborative control; multi-layer verification

摘要： 文章对大众迈腾 B8L 无钥匙进入及启动系统进行研究，探讨无钥匙进入及启动系统的 架构、功能及典型故障诊断方法。KESSY 系统主要由 J965、J519、J285 和天线等多个控制模 块组成，通过控制器局域网（CAN）/局域互联网络（LIN）总线实现模块之间的通信，依托 防盗系统完成多层动态加密验证以实现车门无钥匙解锁、发动机启动。结合具体案例，分析 因 KESSY 控制模块（J965）内部短路导致 CAN 总线电压异常，造成车门无法解锁、发动机 无法启动的故障，通过电压检测、模块插拔与替换等方法定位并修复故障，该案例凸显了 KESSY 系统模块化、网络化和集成化特点对维修人员系统性思维的挑战，为汽车维修提供理 论依据与实践参考。

关键词: 迈腾 B8L；KESSY；协同控制；多层验证