U0401 OBD-II: Invalid Data Received From ECM/PCM "A" OBD-II故障代码U0401是什么意思？
代码 U0401 表示从 ECM/PCM 接收到的数据无效。
发动机控制模块（或动力总成控制模块）是管理发动机运行的计算机。 发动机控制模块（ECM）接收来自全车传感器的输入，然后利用这些信息进行动力总成的特定输出，例如喷油器或线圈组。
在现代车辆中，ECM通过控制器区域网络（CAN）总线与其他模块通信。 而在老式车辆中，模块通常通过更原始的串行数据网络进行通信。 部分原因是老式车辆上的模块数量有限。
CAN网络由两条线组成，分别称为CAN高线和CAN低线。 CAN高线以500k比特/秒的速率传输数据，而CAN低线以125k比特/秒的速率传输数据。 CAN总线的两端有两个终端电阻。
代码 U0401 表示车载一个或多个模块从 ECM 接收到无效数据。
U0401症状
U0401的常见原因
代码U0401通常由以下原因引起：
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如何诊断和维修U0401
进行初步检查
有时U0401会间歇性出现，或者可能是蓄电池没电造成的。 如果该代码是历史代码而不是当前代码，则尤其如此。 清除该代码并查看它是否返回。 如果返回，下一步是进行目视检查。 经过培训的眼睛可以检查诸如断线和连接松动等问题。 如果发现问题，则应修复该问题并清除代码。如果没有任何发现，检查技术服务公告（TSBs）。 TSBs是汽车制造商发布的推荐诊断和维修程序。 查找相关的TSB可以大大减少诊断时间。
检查电池
ECM需要适当的电压才能工作。 在做其他任何事情之前，应检查蓄电池和充电系统是否正常工作，并根据需要进行修理。 然后，清除故障代码并查看故障是否复发。
检查其他DTC
其他故障诊断代码（DTC）可能表明影响 ECM 运行的其他方面存在问题。 例如，多个通信 DTC 可能表明 CAN 网络存在问题。 在诊断 U0401 之前，应解决任何其他 DTC。
See_also: P061C OBD II故障代码 在存储了多个通信DTC的情况下，诊断将转移到CAN总线上。 与任何其他电路一样，可以检查总线是否存在开路和短路等问题。 总线测试通常从数据链路连接器开始，可以使用数字万用表（DMM）或分线盒。 数据链路连接器的6号针脚是CAN高电平，而14号针脚是CAN低电平。 如果出现问题，则需要检查CAN总线。检测到CAN总线故障后，可根据需要进行进一步的测试和维修。
检查控制模块是否故障
如果 U0401 是唯一存储的 DTC，则应检查 ECM 模块本身。 开始此过程的最简单方法是尝试使用诊断扫描工具与 ECM 通信。 一旦连接到车辆，该工具就像网络上的另一个模块。 它可用于寻址 ECM 模块。 如果模块没有响应，则说明其存在问题。
在拆卸模块之前，必须检查其电路。 与其他电子设备一样，ECM模块必须有适当的电源和接地。 这可以使用DMM进行检查。
如果模块的电路正常，但仍无法通信，则可能是模块故障。 但在更换模块之前，应检查其软件。 通常情况下，可以对模块重新编程，而不是更换模块。
See_also: P0339 OBD II故障代码 与U0401相关的其他诊断代码
所有 "U "代码均为网络通信代码。 代码 U0100 至 U0300 为与 XX 模块失去通信的代码。
Ronald Thomas
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