The technical condition of automobiles and assemblies or parts refers to the sum of the appearance, structural performance and technical parameter values that characterize a car, assembly or part at a certain time. Generally divided into intact state, working state and fault state. Technical parameters are divided into structural parameters (size, shape, clearance, etc.), working process parameters (power, fuel consumption, etc.) and accompanying process parameters (heating, vibration, oil containing wear products, etc.). As the mileage of the car increases, the technical parameters change continuously, from the initial value to the allowable value, and finally to the limit value. [1] If the technical parameters of the automobile, assembly or part are between the initial value and the limit value, it is called the working state; if the technical parameter is above the limit value, it is called the fault state; if the technical parameter is between the initial value and the allowable value range, it is called the intact state. The 13th Decree issued by the Ministry of Communications in 1990 stipulates that the technical status of automobiles is divided into four levels.