一辆现代EF索娜塔轿车,在行车中发短速度表突降后自动回升或上下摆动现象,约3～4天出现一次。来厂后,经初检没有再现上述故障现象,但发现车速传感器和速度表已被更换过。根据初检结果,估计该故障最大可能是电路接触不良。为此,首先要进行的工作是对速度表及其传感器的电路进行分析。 速度表及其传感器的电路如图所示。车速传感器为霍尔式传感器,与其连接有3条电线,其一经传感器的2(M/T)或3(A/T)端 A modern EF Sonata sedan, driving in the short speed table after the sudden drop in the automatic rise or swing up and down phenomenon occurs about 3 to 4 days. After the factory, after the initial inspection did not reproduce the above symptoms, but found that the speed sensor and speedometer has been replaced. According to the preliminary results, it is estimated that the maximum failure of the circuit is poor contact. To do this, the first thing to do is to analyze the speedometer and its sensor circuitry. Speedometer and its sensor circuit as shown. The speed sensor is a Hall sensor with three wires connected to it, either on the 2 (M / T) or 3 (A / T) side of the sensor