Automobile diagnostic instruments can only diagnose non mechanical faults. Sensors, communications and control actuators can basically check that they have electricity. Therefore, they can detect and calculate some non electronic fault points. For example, the three-way catalytic converter is damaged. It is possible to analyze the data received by the sensor, but it may still need to be done It can be determined only after the technician's further confirmation. The detection range also depends on the actual demand. For some very simple faults, there is no need to make special detection lines, which will increase the cost and maintenance difficulty. It is mainly considered in reasonable terms. Not every vehicle is the same. The fault diagnosis instrument only extracts the data and fault code provided by the original car computer, and does not have the fault of detecting the engine The barrier function is only to extract data and do some matching, touching and recording of some original computer settings.