汽车网络与总线技术

nullnull汽车网络与总线技术nullCAN Bus Basic Theory基础理论Introduction and History of Data Bus Systems发展史Training ContentCAN Bus Types in VW Vehicles分类CAN Fault Analysis故障 分析 定性数据统计分析pdf销售业绩分析模板建筑结构震害分析销售进度分析表京东商城竞争战略分析 CAN Signal Characteristics信号特性Fault Finding with VAS 5051 and DSO Analysis查询故障 Current Problems Terminal Resistance睡眠模式及终端电阻Future Developments in Data Bus Technology未来发展null基本概念Data Bus: transfer of digital data messages between electronic components on one / two data wire/s using a standardized data protocol 数据公共汽车：根据国际通用数据通信 协议 离婚协议模板下载合伙人协议 下载渠道分销协议免费下载敬业协议下载授课协议下载 ，通过一根或两根数据线，在电控单元间传递数字数据信号 CAN: Controller = control units (CPU’s)控制单元 Area = in the field (= real vehicle), 局域领域 （not a laboratory connection） Network = connected to each other相互连接网络 CAN Bus: serial field bus type using the standardized CAN data protocol 应用标准化CAN数据通信协议通讯系统 Main application area of CAN bus networks:应用领域 CAN is practically a world standard bus type for high speed applications in the industrial area, especially in closed systems - vehicles汽车 - digitally programmed machine tools数控机床 - agriculture machinery、 textile machinery工程机械等null CAN Bus 系统引入安全、舒适及排放方面需求电气元件的增加更多控制单元间大量高速传递需求另外：能实现减轻重量的目标CAN-BUS CAN数据总线可以比作公共汽车。公共汽车可以运输大量乘客，CAN数据总线包含大量的数据信息。 CAN是控制单元区域网络（Controller Area Network）的缩写，意思是控制单元通过网络交换数据。CAN-BUS数据传递原理CAN数据总线的数据传递类似于电话会议一个电话用户（控制单元）将数据“讲”入网络中，其他用户通过网络“接听”这个数据对这个数据感兴趣的用户就会利用该数据，而其他用户则选择忽略数据传递原理nullHistorical Development发展史1983-86 Bosch 软件协议； Intel 控制器 1990 MB S-class with 12 cyl. Engine首次应用于汽车 Audi AG in MY 96 in A8 D2 with 3.7ltr. V8 with 01V AG5大众首次应用 PASSAT B5 AG in MY97; GOLF A4 AG in MY 98 VAN Bus Peugeot标志, Renault雷诺, Citroen雪铁龙等应用 Philips-bus J1850-HBCC Ford with Motorola / Texas Instruments J1850-DLC GM with Motorola / Texas Instruments ABUS Volkswagen with Toshiba东芝 (planned for Corrado but no further development)17年前未应用，null 国际上众多知名汽车公司早在20世纪80年代就积极致力于汽车网络技术的研究及应用，迄今为止，已有多种网络标准。目前存在的多种汽车网络标准，其侧重的功能有所不同。为方便研究和设计应用，SAE车辆网络委员会将汽车数据传输网划分为A、B、C三类。 A类是面向传感器/执行器控制的低速网络，数据传输位速率通常小于10 kb/s，主要用于后视镜调整，电动窗、灯光照明等控制； B类是面向独立模块间数据共享的中速网络，位速率在10-125 kb/s，主要应用于车身电子舒适性模块、仪 表 关于同志近三年现实表现材料材料类招标技术评分表图表与交易pdf视力表打印pdf用图表说话 pdf 显示等系统； C类是面向高速、实时闭环控制的多路传输网，位速率在125 kb/s-1 Mb/s之间，主要用于牵引控制、先进发动机控制、ABS等系统。 nullCAN Bus 优势 Compared with other data bus systems CAN bus networks have the following specific advantages: - high security and reliability level of data transmission数据传递更安全可靠 - low cost of involved components (station connections)低成本 - 高速实时传递 - 有条件实现单线功能 - 适用于各种汽车data protocols are standardized worldwide = ISO 11898 (transmission of information between vehicles of different manufacturers possible) - “open standard” 开放的标准nullExample for Passat B5 with 01V AG5nullExample for Passat B5 with 01V AG5null车门控制单元without CAN完成其全部控制功能需要：45根线和9个插头无CAN 总线：null车门控制单元with CAN完成其全部控制功能只需：最多17 根线，2个插头即可 Data exchange with CAN data bus (low speed CAN) (2 data wires)利用CAN 总线：nullCentral control unit Sensors and Actuators形式1：每项信息通过独立的数据线进行交换。 缺点：线的数量和控制单元插脚增多nullDrivetrain CAN networking with three control unitsDrivetrain CAN active only when terminal 15 is switched on.形式2：各控制单元间的所有信息都通过两根数据线进行交换。CAN-BUS信息交换变速箱控制单元 额定发动机扭矩 额定发动机转速 可执行怠速 转速控制调节 超速切断支持 离合器保护 离合器状态 离合器扭矩 档位变换、动作/不动作 压缩机切断 换档杆位置/行驶位置 汽车车速 档位指示 当前档位或目标档位 发动机控制单元编码 应急运行程序（自诊断信息） 车载诊断状态发动机控制单元 发动机转速 额定怠速转速 实际发动机扭矩 冷却液温度 强制减档信息 加速踏板位置 制动灯开关 制动踏板开关 进气温度 CCS状态（定速巡航） CCS额定车速 海拔高度信息 空调压缩机状态 应急运行程序（自诊断信息）ESP控制单元 TCS要求 EBC要求 ABS应用 EDL介入 DSP介入车轮转速，左前 车轮转速，右前 车轮转速，左后 车轮转速，右后CAN（高）CAN（低）变速箱控制单元发送信息变速箱控制单元接受和计算信息CAN-BUS信息交换null数据总线基本原理null自动箱控制单元ABS控制单元发动机控制单元？？？优先权？Data bus wiresCAN 数据传输总线null优先权控制单元...信息传递1234ABS/EDL 控制单元发动机控制单元发动机控制单元自动箱控制单元- Engine Braking Ctrl. - Traction Control requirement- Engine speed- Throttle valve position- Kickdown- Coolant temperature- Vehicle speed- Selector lever position- Gearbox in emergency running- Driving range changenullMain Characteristics主要特性串行接口 = 信息传递有次序性 控制单元的平等性 广发性： 优先性：大众与博许共同定义 周期性与重复性： nullnull技术数据可能的最高传播速度 1 Mbps = 1 Megabit per sec. = 1 000 000 bPS ISO 分类 high speed bus type > 125 000 bps low speed bus type \< 125 000 bps 一个完整的信息传播周期 ca. 1 msec. (depending of data field length) 最多接入控制单元数 32 最长一根 CAN bus 线长度 40 m 通用版本 Bosch CAN 2.0 bps = bits per second 8 bits = 1 Byte 1 Mbps = 1 000 kbps = 1 000 000 bpsnullCAN Bus Basic Theory基本原理模拟信号Pulse Width Modulated 脉宽调制信号数字信号每根线一个信号每根线传递2-3个信号无限（ 2048=211)以电压电阻为基础基于占空比1S基于二进制数字二进制数字bit = “binary digit” = one circuit state per time unit = smallest possible information unit高压传感器高压传感器调节比率20%-25%调节比率20%-25%nullnullBinary Number System二进制系统- bits are defined as the basic states or values of the binary number system - the binary number system is a number system which is built up on the base 2 and uses only two different digits 0 and 1 = binary digits Advantage of the binary system: simplicity (only two different numbers) Problem of the binary system: length of the numbers Because of the simplicity the binary system today is used to process and exchange data information (= messages) in digital shape in electronic computer systems Binary 0 = 0 x 20 = Decimal 0 Binary 1 = 1 x 20 = Decimal 1 technically one bit can have two logical or electrical states: 1 = “yes” = x Volt 0 = “no” = 0 VoltnullBinary and Decimal System二进制和十进制In difference to the binary system the decimal number system is using 10 digits (from 0 - 9) and is built up on the base 10. The value of the position rises for both systems from right to left: Example for binary system: Binary number 10101 1 0 1 0 1 1 x 20 = 1 x 1 = 1 0 x 21 = 0 x 2 = 0 1 x 22 = 1 x 4 = 4 0 x 23 = 0 x 8 = 0 1 x 24 = 1 x 16 = 16 21 dec.Example for decimal system: Decimal number 12789 1 2 7 8 9 9 x 100 = 9 x 1 = 9 8 x 101 = 8 x 10 = 80 7 x 102 = 7 x 100 = 700 2 x 103 = 2 x 1000 = 2000 1 x 104 = 1 x 10000 = 10000 12789 dec.nullBinary and Hexadecimal System二进制和十六进制The hexadecimal system is using 16 digits (from 0 - F) and is built up on the base 16. The value of the position rises also from right to left: Hexadec. Dec. A = 10 B = 11 C = 12 D = 13 E = 14 F = 15 Example for hexadecimal system: Hexadecimal number 3AB7 3 A B 7 7 x 160 = 7 x 1 = 7 11 x 161 = 11 x 16 = 176 10 x 162 = 10 x 256 = 2560 3 x 163 = 3 x 4096 = 12288 15031 dec.nullDecimal to binary十进制-二进制 12 12 : 2 = 6 Rest 0 6 : 2 = 3 Rest 0 3 : 2 = 1 Rest 1 1 : 2 = 0 Rest 1 1 1 0 0Conversion Examples转换举例Binary to 二进制-十进制decimal 1 1 0 0 0 x 20 = 0 x 1 = 0 0 x 21 = 0 x 2 = 0 1 x 22 = 1 x 4 = 4 1 x 23 = 1 x 8 = 8 12 Hexadecimal to decimal16进制-10进制 2 A 5 E E x 160 = 14 x 1 = 14 5 x 161 = 5 x 16 = 80 A x 162 = 10 x 256 = 2560 2 x 163 = 2 x 4096 = 8192 10846 dec.nullCorrelation Chart 转换表nullBinary Coding二进制代码CAN bus 以很长的字符串定义单个信息Each additional bit doubles the number of possible signal values !null8 Bit MessageExample for usage of a 8 bit message to code the coolant temperature of a vehicle:With 8 bits it is possible to code 256 different values of one messagenullData Protocol数据格式The CAN Data Protocol (当前 2.0) is the standard format which defines how a complete message (= string of bits) is transferred on the CAN bus network. It is subdivided in seven fields (message data frame): 每个信息由七个部分构成，这就是信息的基本框架称为数据域。Start field (length = 1 bit)开始域Control field (6 bit) 控制域Data field (max. 64 bit) 数据域CRC Safety field (16 bit) 安全域Acknowledge field (2 bit)检验域End field (7 bit) 结束域Arbitration field (12 bit) 状态域（11）CAN bus信息极限 108 bit nullField Description 1数据域属性Start Field start of the data protocol for every message to be sent on the CAN bus (start field is also called “Start of frame” SOF), always dominant bit Function: synchronization of the participating control units 开始域 信息格式的开始，将要发数据往CAN-BUS的标志。大小为一位，状态为显性 Arbitration consists the message identifier (11 bits) and the RTR bit (= remote Field transmission request); the arbitration field defines the priority ranking of the following message and the RTR bit shows if the message is a data message or a so called remote frame (= no data bytes included)决 定状态域 数据的优先权，大小为11位纯数据 Control Field shows in the last four bits the length of transferred data (in bytes) in the following data field (4 bits, e.g. if 0100 = 4 bytes, 0101 = 5 bytes); the first bit is the IDE controller showing if standard data length or extended data length, the second bit is currently not in use 控制域（检查域）：表示数据的 大小即字节长度（显示数据域中包含的信息项目） Data Field contains the data transferred onto the CAN bus (max. 64 bit = 8 byte), the meaning of each bit is assigned during the technical development of the control unit (different signals can be included in one data field); 数据域 被传递到其他控制单元的信息所在位置（在此信息被传到其他控制单元） nullField Description数据域属性2CRC Field Cyclic Redundancy Check; field is used for the calculation of a statistical checksum over all data bits in the sent message; the receiving control units are also calculating this checksum over all data bits in the received message and are then comparing both results; it is used to detect erroneous bits in a message（16） 安全域 发射数据和接收信息的控制单元检查和比较传递数据所发生变化的错误（检测传递数据中的错误） Acknowledge in this 2 bit field every control unit is confirming the correct reception Field of the data message (comparison of the checksums) 确认域 每个控制单元，通过这两位被确认已经正确接受信息，否则将重发数据。 End Field every message is completed by a series of 7 recessive bits, also called “End of frame” (EOF) 结束域 通过7位隐形显示，表示该信息数据传递结束，这里是显示错误并重发送数据的最后一次机会。nullCAN Bus Hardware硬件CAN Components: Data bus terminal resistor终端电阻Data bus wire传输线Electronic control unit for automatic transmission J217 with CAN controller and CAN transceiver带控制器和收发器的控制单元Motronic electronic control unit J220 with CAN controller and CAN transceiver带控制器和收发器的控制单元 a controller控制器 a transceiver收发器 two data bus terminal resistors两个终端电阻 two data bus lines.两条传输线Data bus terminal resistor终端电阻nullComponents部件功能The CAN controller控制器 接收在控制单元微处理器中传递的数据信号，然后传递它们到收发器；并能反向传递。The CAN transceiver收发器 is a combination of a transmitter and a receiver.一个发射器和一个接收器的组合。 It converts data from the CAN controller into electrical signals for transmission via the so called TX line through to the data bus lines.收发器将从控制器接收的数据转化成能够通过can-bus传递的电信号。并能反向传递。The data bus lines传输线 are bi-directional and are used to transmit the data.被用于双向传输数据的导线 They are identified as “CAN High” and “CAN Low”.被定义为高位和地位The data bus end terminal (Matching resistors)终端电阻 是一个电阻器，防止数据传输终了时，被反射回来，产生波形叠加破坏数据。nullData Transmission Process数据传递过程Data bus lineElectronic control unit 1Electronic control unit 2Electronic control unit 3Electronic control unit 4Data acceptanceData acceptanceData supplyData checkData receptionData checkData checkData receptionData receptionData transmissionnullBit Value Generation数据（位）值的定义一位数据在逻辑上和电学上，只能是两种状态（0 或 1），其中的一种 状态值的含义 “1“ 开关闭合 灯泡点亮状态值的含义“0“ 开关打开 灯泡熄灭CAN bus 逻辑值 1 x Volt 0 VoltCAN bus逻辑值 0 x Volt 0 VoltCAN bus 发射器 产生逻辑值，其作用相当于开关nullNegative Logic Principle反逻辑原理实际上当前在 CAN bus 在数据信息字节定义采用反逻辑原理 开关闭合 灯泡熄灭 显性信号 开关打开 灯泡点亮 隐形信号CAN 状态值 发射器关闭 CAN-BUS线上电压 ca. 1 V or 3 V 舒适 bus ca. 1.5 or 3.5 V 驱动 busCAN状态值 发射器打开 CAN-BUS线上电压 ca. 0 V or 5 V (12 V) 舒适 bus ca. 2.5 V 驱动 busnull0 Bit Dominance字节0的显性特性nullArbitration Process优先权判定所有控制单元同时开始向CAN-BUS发射信息避免数据碰撞，在12位的状态域中预先定义数据的优先权 发射隐性电位的控制单元，若检测到一个显性电压，那么该控制单元停止发射转为接收Recessive bit = lower priorityAG 4/5 control unit becomes receiverAG 4/5 messageABS / ESP messageECU messageECU becomes receiverDominant bit = higher priority“Smallest number wins”nullNoise and Interference Problems噪音和干扰问 题 快递公司问题件快递公司问题件货款处理关于圆的周长面积重点题型关于解方程组的题及答案关于南海问题 两条数据线相互缠绕，防止电磁波干扰和向外辐射两条数据线传递相同信号，但数值互为镜像。nullCAN Bus Types in VW Vehicles大众车CAN BUS 分类drive train CAN bus (Bosch) 500 kbit / s convenience CAN bus (VW) 100 kbit / s infotainment (display) CAN bus (VW) 100 kbit / s 系统容量所限 (max. 32 units) 故障的关联性要求 (esp. for Conv. CAN and Infot. CAN) 历史发展: different data speed and voltage 成本问题: controller and transceiver for low speed data busses are cheapernullI-Pump ( V6 TDI )EngineAutomatic Transm.ABSAirbagSteering SensorCAN- Drive trainDoor CU LFDoor CU RFDoor CU RRDoor CU LR ZM Centr.LockMemoryLow - SpeedGatewaynullnullCAN 数据总线网络 连接部件驱动 CAN bus舒适 CAN bus显示（信息娱乐） CAN bus发动机控制单元自动变速器控制单元ESP控制单元安全气囊控制单元氧传感器（美国）转向角度传感器转向柱电气控制单元多功能方向盘控制单元汽车电气控制单元座椅调节控制单元停车辅助控制单元挂车识别控制单元空调控制单元驻车加热控制单元轮胎压力监控控制单元舒适系统中央控制单元语音输入控制单元卡片阅读器远程通讯、电话控制单元车载电话控制单元收音机导航系统控制单元导航、电视等导航系统接口nullCAN DiagnosticsCAN ComfortCAN InfotainmentCAN Combi开笛（PQ35） CAN 系统Gateway Control UnitCAN DrivenullMotor CU 发动机Brake CU 制动系统Airbag CU 气囊Steering boost sensor转向角Electric steering 电子转向助力GatewayCAN systemnull收音机导航 Radio/RNS 2界面 Interface Box停车加热Parking heaterCAN “Infotainment” networkGatewayCAN system networknull能量供给 Power Supply System CU转向柱开关 Steering column switch module拖车控制单元 Trailer CU仪表Multi-function CU空调Air-con. CUCAN “Comfort” networkGatewayWipers雨刮CAN system networknull司机门控制单元 Driver door CU副司机门控制单元 Passenger door CU舒适系统控制单元 Comfort CUCAN “Comfort” network隔离栅监控 Passenger compartment monitoringCAN system networknullDriveCombiComfortInfotainmentDiagnosticorange/brown桔/棕 orange/black桔/黑orange/brown桔/棕 orange/green桔/绿orange/brown桔/棕 orange/violet桔/紫罗兰orange/brown桔/棕 orange/red桔/红orange/brown桔/棕 orange/blue桔/兰purple/blue紫/兰Cable colours in CAN 线色CAN LowCAN system networkCAN HighnullDrive Train CAN Bus动力总线Main Characteristics:主要特征 - Data speed: 500 000 bps (= high speed CAN bus) - Duration of 1 bit transfer: 0.002 msec. (one message ca. 0.2 msec) - Basic voltage in idle mode (no data transfer): ca. 2.5 Volt against earth on both wires - Transmission cycle of messages to the CAN bus line: between 7 – 20 msec. (this depends of the current engine speed, because the transmission cycle is fixed to the crankshaft rotation under real time conditions) - 线色: CAN-H = orange-black桔黑 CAN-L = orange-brown桔棕 - Line diameter线径: 0.35 mm2 Line hubs in CFD节点: CAN-H CAN-L - No single wire mode possible 无单线工作模式A121A122nullConvenience CAN Bus舒适总线Main Characteristics主要特征: - Data speed: 100 000 bps (= low speed CAN bus) - Duration of 1 bit transfer: 0.010 msec. (one message ca. 1.1 msec) - Basic voltage in idle mode (no data transfer): CAN-H = 0 V CAN-L = 5 V (12 V) - Transmission cycle of messages to the CAN bus line: every 20 msec. or event controlled - Line colors: high wire CAN-H = orange-green low wire CAN-L = orange-brown - Line diameter线径: 0.35 mm2 Line hubs in CFD节点: CAN-H CAN-L - Single wire mode possible可能单线工作 A146A147nullInfotainment CAN Bus信息总线Main Characteristics主要特征: - Data speed: 100 000 bps (= low speed CAN bus) - Duration of 1 bit transfer: 0.010 msec. (one message ca. 1.1 msec) - Basic voltage in idle mode (no data transfer): CAN-H = 0 V CAN-L = 5 V (12 V) - Transmission cycle of messages to the CAN bus line: every 20 msec. or event controlled - Line colors: high wire CAN-H = orange-lilac low wire CAN-L = orange-brown - Line diameter线径: 0.35 mm2 Line hubs in CFD节点: CAN-H CAN-L - Single wire mode possible可能单线工作 A178A179null中央线束连接（星形接法）左侧A柱 白色插头T10W/2、3（80-120） 舒适系统数据总线 (orange-green) 信息娱乐系统数据总线 (orange-violet)驱动数据总线 (orange-black)右侧A柱 仪表台右侧线束内J234G85J217J285J104J220CAN 数据总线网络nullCAN Bus 线束维修 1Never disconnect the central wiring hubs by opening or cutting of the crimps !!!Wiring connectors are critical components in defining in-line signal reflection – this is why they should not be opened. The wiring connectors are not available as spare parts !nullCAN Bus 线束维修 2Repair of CAN bus wiring is permitted only if use VAS 1978 !!!Untwist for max. 50mm> 100mmCAN repair wire P/N: 000 979 987 10 m roll green-yellow and white- yellow twisted cable 0.35mm2 Standard twist length: 20mmnull 仪表内的 Gateway自动变速箱控制单元 J217舒适系统中央控制单元 J393Control unit for 4LV J537仪表内的诊断接口 J285空调控制单元 E87Data telegramGateway 的作用是使所有连接在CAN总线上的控制单元实现数据交换 驱动总线 舒适总线和 显示总线 (信息娱乐总线). 因为这几种总线的传输速度是不同的，所以不能直接进行数据交换。 VAS5051： 9600/10400 baudCAN 数据总线网络 Gatewaynull第一种诊断接口 (Gateway) = 实际控制单元 (软件) 安装在 仪表 内诊断接口 (Gateway)null第二种 Skoda (Fabia) gateway 在汽车电气控制单元内 Polo 2002年型 也安装在汽车电气控制单元内.汽车电气控制单元Gatewaynull作用作为诊断 gateway...作为数据 gateway…使连接在不同的数据总线上的 控制单元能够交换数据Gateway在不改变数据的情况下，将驱动总线、舒适总线、信息娱乐总线的诊断信息传递到K线。nullGateway Diagnostic Interface网关诊断接口Drive train CANConve-nience CANK-wire to diagnostic plugJ285 + J533CPU-dashDATA-GatewayDIAGNOSIS-GatewayController 单独自诊断地址码 (19) Drive train CANnullGateway Connection at VW VehiclesThe connection is shown in principle, the self diagnosis via CAN protocol is not yet in use and will be introduced later19 2027 288 9Plug T32b ( green )Diagnostic plugK-wire25Plug T32a ( blue )CAN diagnosisDrive Train CANConvenience CAN 7 8 9! not yet in use !nullCAN Bus Network Examples Examples for possible operation paths (signal routing) with CAN bus systems: - dual tone horn operation - windscreen wiper operation - cruise control operation - turning light operation - parking light operation - hazard warning light operation - lighting control oldnewOne or more operating and monitoring control units connected via CAN bus nullCAN Fault Analysis故障分析first: always check the coding values if all installed control units are correctly coded plus verification of correct dash insert part number and coding (esp. country code, if available) 首先检查编码 - second: check the fault memory of all control units 其次：检查所有控制单元的故障记忆 - third: before checking CAN bus wiring and control unit communication always check the incoming signals from sensors and outgoing signals to actuators in the respective measuring value blocks and via final control diagnosis 第三：在各个控制单元检查传感器执行元件初始信号 - fourth: check the CAN bus wiring and communication with DSO and / or Multimeter 最后：用DSO或万用表检查CAN BUS线和数据信息02 fault memory 07 coding08 read data blocks03 final control diagnosisnullCauses for Single Wire Mode单线工作模式的成因 整个 CAN bus永久单线: - short circuit CAN high to CAN low - short circuit CAN high to plus - short circuit CAN high to earth - short circuit CAN low to plus - short circuit CAN low to earth CAN bus交变单线（部分单线）Following defects are causing an alternating “Single Wire” mode (only part of the CAN bus changes to “Single Wire” mode): - open circuit in CAN high to a control unit - open circuit in CAN low to a control unit Open circuits generate an alternating displayShort circuits generate a permanent displaynullFault Type Analysis 故障分析1All CAN bus wiring interruptions can be usually detected via systematic analysis of the fault types registered in the respective control units (use of DSO signal analysis normally not necessary) 所有CAN bus断通常能够由各自控制单元自诊断识别。 Both CAN wires in Convenience and Infotainment CAN bus are interrupted: 舒适和信息总线两条线被断开，故障信息如下： - Fault type: “communication to control unit xxx not possible” One wire in Convenience and Infotainment CAN bus is interrupted: 舒适和信息总线一条线被断开，故障信息如下： - Fault type: “CAN bus to control unit xxx in single wire mode” 识别为单线2秒后，形成故障记忆 Single wire mode fault will be set only if recognized for > 2 sec. ! One or both wires in Drive Train CAN bus are interrupted: 动力总线中一或两条线被断开，故障信息如下： - Fault type: Communication to control unit xxx not possible” nullFault Type Analysis故障分析2All CAN bus wiring short circuits usually have