Oxygen Sensor Diagnosis And Cleaning

The oxygen sensor feedbacks the concentration information of the mixture to the ECU by detecting the oxygen content in the engine exhaust gas. It is installed on the exhaust pipe before the three-way catalyst.
The sensitive element used for generating voltage signals in oxygen sensors is zirconia (ZrO2), which has a layer of platinum on its outer surface and a layer of ceramic on the outside of the platinum to protect the platinum electrode. The inner side of the oxygen sensor sensitive component is open to the atmosphere, while the outer side is discharged through the exhaust gas from the engine. When the temperature of the sensitive component is above 300 ℃, if there is a significant difference in oxygen content on both sides, an electromotive force will be generated on both sides. The inner side of the sensitive component has a high oxygen content due to being exposed to the atmosphere. When the mixture is lean, the oxygen content in the exhaust gas is higher. The difference in oxygen content on both sides of the sensitive element is very small, so the generated electromotive force is also very small (about 0.1V); When the mixture is too rich, the oxygen content in the exhaust gas is very low, and the difference in oxygen concentration on both sides of the sensitive element is large, resulting in a larger electromotive force (about 0.8V). The heater inside the oxygen sensor is used to heat sensitive components to ensure their normal operation.
If the oxygen sensor has no signal output or the output signal is abnormal, it will increase engine fuel consumption and exhaust pollution, resulting in unstable idle, misfire, and chattering. Common faults of oxygen sensors include:
1) Manganese poisoning, although leaded gasoline is no longer used, the anti knock agent in gasoline contains manganese. After combustion, manganese ions or manganese oxide ions adhere to the surface of the oxygen sensor, making it unable to generate normal signals.
2) Carbon accumulation, the platinum surface area of the oxygen sensor cannot generate a normal voltage signal after carbon deposition.
3) Poor contact or open circuit in the internal wiring of the oxygen sensor without signal voltage output.
4) The ceramic components of the oxygen sensor are damaged and cannot generate a normal voltage signal.
5) The resistance wire of the oxygen sensor heater is burnt out or its circuit is open, which prevents the oxygen sensor from quickly reaching normal operating temperature.