Failure: a Mercedes-Benz W211E240 sedan, the user reflects the car's KEYLESSGO function (vehicle keyless control system) reaction is not sensitive enough, and sometimes the use of KG lock car, the door system slow response, only the implementation of multiple operations to complete the normal operation of the situation The
    Maintenance personnel on the car for the KG function test to confirm the vehicle does exist the user described the fault symptoms, but also found that when the KG system reflects the slow, the instrument multi-function display will appear "KEYNOTRECOGNITION" prompt.
    According to the previous maintenance experience, maintenance personnel on the KG system for computer testing, but the relevant system control unit without fault display, and the actual value and coding CODE completely correct. The author consulted the maintenance manual and found that the KG system related to the control unit up to 7. (N102) plays an important role in the system, which is the center of the KG card and the ignition lock EIS. The maintenance unit of the control unit (N102) plays a vital role in the system. According to the working principle of the system analysis, maintenance personnel to exclude the other five control unit failure of the possibility, so the focus will be on the ignition lock EIS and N102 these two control units. Maintenance personnel use the Mercedes-Benz oscilloscope HMS90 to test the computer data transmission system, after several waveform capture and found that N102 sometimes can not normally transfer the driver to implement the lock car or drive command information (fault waveform and the normal waveform is different ). So I determine the rear KG control unit of their own electrical problems or software problems, resulting in the system can not work properly, resulting in the user described the failure. The final replacement N102 and functional testing, troubleshooting.
    Review Summary: As the vehicle on the electrical equipment more and more complex, network, so in the maintenance of these vehicles, should not only repair a point, but should grasp the working principle of the relevant system to do a comprehensive analysis.