变速箱的控制单元从安装在变速箱上和车辆上的诸多传感器如：车速传感器、变速箱输入转速传感器、变速箱输出转速传感器、发动机转速传感器、油门踏板位置传感器等等采集信号，经过数据处理后发送指令给执行机构如：电磁阀N88-N94,从而控制相应的换挡离合器或制动带工作使变速箱换入相应的档位。

The control unit of the gearbox collects signals from various sensors installed on the gearbox and vehicle, such as the vehicle speed sensor, gearbox input speed sensor, gearbox output speed sensor, engine speed sensor, accelerator pedal position sensor, etc. After data processing, it sends instructions to the executing mechanism, such as solenoid valve N88-N94, to control the corresponding shift clutch or brake band to work and shift the gearbox into the corresponding gear.

本案例的故障出现在电控系统部分，产生故障码“17105 P0721 035-输出转速传感器电路范围/性能间隙式”的原因分析如下：

The fault in this case occurred in the electronic control system, and the cause of the fault code "17105 P0721 035 Output Speed Sensor Circuit Range/Performance Gap Type" is analyzed as follows:

(1)按照正常的信号处理顺序：车速信号首先进入到仪表，经过仪表控制单元进行处理后通过CAN数据总线送给各个ECU。变速箱的ECU从CAN数据总线上取得车速信号进行换挡控制。

(1) According to the normal signal processing sequence: the vehicle speed signal first enters the instrument panel, and after being processed by the instrument control unit, it is sent to various ECUs through the CAN data bus. The ECU of the gearbox obtains the vehicle speed signal from the CAN data bus for gear shift control.

(2) G38是输出转速传感器，它和输入转速传感器G 192配合计算现在的档位，为下次换挡做准备。发动机转速和车速是变速箱进行换挡控制的两个主要数据，当变速箱的ECU无法识别车速时，换挡也就无从操控，变速箱将进入到紧急运行功能中。

(2) G38 is an output speed sensor that works in conjunction with input speed sensor G 192 to calculate the current gear position and prepare for the next gear shift. The engine speed and vehicle speed are the two main data for shifting control of the gearbox. When the ECU of the gearbox cannot recognize the vehicle speed, shifting cannot be controlled, and the gearbox will enter the emergency operation function.

(3)变速箱根据发动机转速信号、变速箱输入转速G 182的信号和输出转速G38的信号，结合车速传感器G22的信号决定换挡。但是此时车速信号变换不定：从0-255-154-80公里/小时等乱变，因此在换挡程序设定的范围内ECU无法判断清楚，故给出了上述故障码。

(3) The gearbox determines gear shifting based on the engine speed signal, the input speed signal G 182, and the output speed signal G38, combined with the signal from the vehicle speed sensor G22. However, at this time, the speed signal changes unpredictably, ranging from 0-255-154-80 kilometers per hour, etc. Therefore, the ECU cannot determine clearly within the range set by the gear shift program, and the above fault code is given.

(4)由于大灯控制单元浸泡在水中，导致CAN数据总线工作失常，进而影响到车速信号的正确发送，当车速信号发送正确时，变速箱工作正常；当车速信号发送不正确时，变速箱工作不正常。因而会有变速箱问歇性的故障。经过观察分析，我们发现车辆的后风挡玻璃在贴太阳膜时喷的水最后都流进了大灯控制单元里，导致了变速箱的工作不正常。

(4) Due to the headlight control unit being immersed in water, the CAN data bus malfunctioned, which in turn affected the correct transmission of the vehicle speed signal. When the vehicle speed signal is transmitted correctly, the gearbox works normally; When the vehicle speed signal is sent incorrectly, the gearbox is not working properly. Therefore, there may be intermittent faults in the gearbox. After observation and analysis, we found that the water sprayed on the rear windshield of the vehicle when applying the solar film eventually flowed into the headlight control unit, causing abnormal operation of the gearbox.