The four wires of the automobile oxygen sensor plug are divided into two types: heating wire and signal wire. Heating wire refers to the heating coil power supply and grounding wire connected to the engine computer, which can make the automobile oxygen sensor enter the working state faster. As for the remaining two signal lines, they are connected to the driving power supply to control the air-fuel ratio of the automobile, thus improving the fuel combustion quality of the automobile engine. The method of detecting oxygen sensor is relatively simple. Firstly, connect two probes of a multimeter to two signal lines of the oxygen sensor (red pen to the signal positive electrode and black pen to the signal negative electrode). Then directly observe the voltage change of the multimeter, and the normal signal voltage range is 0.1~ 0.9v. Secondly, the faster the voltage frequency of the oxygen sensor changes, the better the sensor. Then, if the voltage is 0v or 1v, or even there is no change, it means that the oxygen sensor at this time is seriously aging and needs to be replaced in time.