The mileage is about 10 thousand km, the chassis number is LE42121479, and the Mercedes E260 car with a sliding panoramic skylight is installed. The user reflects: the car skylight can't work. Fault diagnosis: after the car, first test the car to verify the fault, found the sunshade in the sunshade in the half open position, but the operation of the skylight switch, sun shade and skylight no action. According to relevant information, the sliding panoramic sunroof assembled by the vehicle consists of two parts: electric skylight and electric sun shading curtain. When the operating skylight opens the switch (integrated on the roof control unit), the sun shade begins to roll first and then the skylight will open; when the operating skylight closes the switch, the skylight is closed first, and the sun shade will unfold. As long as the continuous acceleration of the skylight switch exceeds 40 ms, the actuating signal can be detected. 2 Holzer sensors are installed on the skylight motor and the sun shade motor, and the 2 Holzer sensors are offset 90 degrees. The panoramic sliding window control unit (integrated on the skylight motor) calculates the speed of the skylight motor and the sun shade motor by monitoring the pulse number of the Holzer sensor, so as to judge the skylight and the sun shade. Position. Besides, the system also has the functions of overheating protection, anti blocking and anti clamping. The panoramic sliding window control unit estimates the temperature of the motor by monitoring the voltage, current, driving time and the temperature of the outside of the sun shade motor to protect the motor by monitoring the voltage, current, time and temperature of the sun shade motor. The panoramic sliding skylight control unit monitors the speed of the skylight motor and the shade motor during the reception of the skylight request, and compares it with the related parameters of the teaching mode. If the comparison results exceed the specific limit, the panoramic sliding skylight or shade curtain is blocked (panoramic sliding skylight). The control unit can automatically adapt to the increase of inflexibility, such as the change of speed caused by dirt in the mechanical system. If the obstruction is detected during the closing of the skylight or sunshade curtain, the drive of the skylight motor or the sun shade motor will be interrupted and the reverse movement begins (the anti clamping function starts); if the obstruction is detected during the opening process, it will only interrupt the driving sun curtain motor or the skylight motor. After understanding the characteristics of the panoramic sliding skylight, the vehicle can be targeted for troubleshooting. Connect the fault detector, test the vehicle quickly, read the fault code stored in the control unit of the panoramic sliding roof window, as shown in Figure 1. Refer to the 3 fault code bootloader, it is recommended to implement the standardized operation of sliding sunroof and sunshade curtain. As a result, the panoramic sliding skylight and its sunshade curtain were standardized, and the sun shades and skylights were found to be unable to move. The fault detector indicated that the anti clamp protection sensor was not successful in learning. Activate the skylight with the activation function of the fault detector, and the skylight can act. But when the sun shade is activated, there is no response to the sun shade. Because the sun shading curtain is half open, the primary task is to open or close the sun blind. Referring to the relevant circuit, the skylight switch sends the signal to the panoramic sliding window control unit, and then controls the opening or closing of the sun curtain and the skylight by the panoramic sliding window control unit. According to the hint that the fault code has been locked on the shading curtain actuator, it is deduced that the sun screen motor is damaged. After trying to replace the sun shading curtain motor with the normal vehicle, it is found that the sunshade curtain is still not moving, and the fault code remains unchanged. The skylight motor is integrated with panoramic skylight control unit, which is used to monitor the sun shade motor. It is suspected that the integrated panoramic sliding window control unit on the skylight motor has a fault, and it is mistaken for the sun shade motor to be locked. So the sun switch motor was replaced and the sun shade was restored to normal. Troubleshooting: according to the above test results, it can be determined that the internal fault of the sunroof motor causes failure. No spare parts of sunroof motor can be replaced in factory, order from manufacturer, after replacement of sunroof motor, the trouble is completely eliminated.