1. Carbon deposition

Due to the poor combustion of the engine, carbon deposits are formed on the surface of the oxygen sensor, or deposits such as oil stains or dust enter the oxygen sensor, which will hinder or block the outside air from entering the oxygen sensor, making the output signal of the oxygen sensor inaccurate, and the ECU cannot correct the air-fuel ratio in time. Carbon deposition is mainly manifested in the increase of fuel consumption and the obvious increase of emission concentration. At this time, if the sediment is removed, it will resume normal work.

2. Ceramic fragmentation of oxygen sensor

The ceramic of oxygen sensor is hard and brittle, and it may break and fail if it is knocked with a hard object or washed with strong airflow. Therefore, special care should be taken when handling, and problems should be replaced in time.

3. The heater resistance wire is burnt out

For the heated oxygen sensor, if the heater resistance wire is ablated, it is difficult to make the sensor reach the normal working temperature and lose its function.

4. The internal circuit of oxygen sensor is broken.

5.Inspection of appearance color of oxygen sensor

Remove the oxygen sensor from the exhaust pipe, and check whether the vent hole on the sensor housing is blocked and the ceramic core is damaged. If it is damaged, replace the oxygen sensor.

The fault can also be judged by observing the color of the tip of the oxygen sensor:

① Light gray tip: This is the normal color of oxygen sensor;

② White tip: It is caused by silicon pollution, and the oxygen sensor must be replaced at this time;

③ Brown tip: It is caused by lead pollution. If it is serious, the oxygen sensor must also be replaced;

④ Black tip: It is caused by carbon deposit. After the engine carbon deposit fault is eliminated, the carbon deposit on the oxygen sensor can be removed automatically.

The main oxygen sensor includes a heating rod for heating the zirconia element. The heating rod is controlled by the computer (ECU). When the air intake is small (the exhaust temperature is low), the current flows to the heating rod to heat the sensor, so that the oxygen concentration can be accurately detected.

Platinum electrodes are arranged on the inner and outer sides of the tube-shaped zirconium element (ZRO2 _ 2). In order to protect the platinum electrodes, the outer side of the motor is covered with ceramics, and the oxygen concentration in the inner side is higher than the atmosphere, while the oxygen concentration in the outer side is lower than the automobile exhaust gas concentration.