Fault 1: The vehicle deviates greatly from the correct position.
    A VIA car, the user reflects the actual location of the car in Beijing near the South Third Ring Road Liujiayao overpass, and the vehicle on the map shows the vehicle is located in Beijing Tongzhou District, near the North Island, the navigation system without sound guidance.
    After inspection, the car's failure as described by the user. According to the fault of the car, start the vehicle first, turn on the GPS receiving power switch, and make the navigation system display the map, and then drive the vehicle to a good field of view on the open field and check whether the "GPS" mark is displayed. The inspection found that the car's navigation system can only display the map, can not display "GPS" mark. Subsequently, the correct position of the vehicle is corrected according to the procedure of the driver's manual.
    As the car equipped with GPS navigation system with self-diagnostic function, decided to first self-diagnosis of the navigation system. (ACC position can also be), and then press the INFO switch on the multi-function display, control the wide light switch, through the switch from the brake switch, open the ignition switch to the ON position (ACC position can also) OFF-TAIL-OFF-TAIL-OFF-TAIL-OFF-TAIL-OFF, the system has entered the fault diagnosis interface. It has been observed that there is a bad fault code in the system, and the fault code is checked and recorded.
    After the fault code is cleared, the road test is performed and the fault occurs again. According to the fault code of the bad speed signal, consult the relevant maintenance manual. In accordance with the requirements of the maintenance manual, you should first check the vehicle speed input signal is normal, and GPS self-diagnosis system speed signal comparison to confirm whether the speed is consistent. If there is a large error, you need to use the oscilloscope to check the speed of the waveform, but also should further check the speed sensor and the relevant line is normal.
    When it is determined that there is no problem with the vehicle speed signal, it is decided to check whether there are other optical components (radar tester) on the vehicle, whether the oil mist is attached to the window, or any metal material is adsorbed on the instrument panel. The inspection found that the car is equipped with radar detectors, and in the windows and the front windshield glass with anti-explosion film. After the GPS satellite receiving antenna is guided to the outside of the vehicle with a dedicated connecting line, the road map is displayed. The result shows that the position on the map coincides with the actual position of the vehicle, but the navigation system still has no sound guidance.
    As the sound of the navigation system is issued by the speaker, according to the requirements of the maintenance manual, decided to check the navigation system to provide the sound of the left side of the vehicle speakers. With the radio test, the loudspeaker can sound normally and use a multimeter to measure the resistance of the loudspeaker to 4Ω. Therefore, it is possible to make sure that the speaker is fault-free and that the relevant line is checked according to the requirements of the maintenance manual, but no abnormality is found. At this point, to determine the fault should be in the navigation system itself. Replace the navigation system ECU after troubleshooting.