Remove the oxygen sensor from the exhaust pipe and check the vent hole on the sensor casing for blockage and damage to the ceramic core. If it is damaged, the oxygen sensor should be replaced.
The fault can also be judged by observing the color of the top part of the oxygen sensor:
1, light gray top: this is the normal color of the oxygen sensor;
2, white top: caused by silicon pollution, at this time must replace the oxygen sensor;
3, brown top (as shown): caused by lead pollution, if serious, must also replace the oxygen sensor;
4, black top: caused by carbon deposits, after eliminating engine carbon deposit failure, generally can automatically remove carbon deposits on the oxygen sensor.