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The function and detection method of the car oxygen sensor, how to judge the oxygen sensor is broken

The role of car oxygen sensor

Cars usually have two oxygen sensors, a front oxygen sensor and a rear oxygen sensor. The front oxygen sensor is generally installed on the exhaust manifold, and the rear oxygen sensor is installed behind the three-way catalytic converter. Their respective roles in the exhaust system are different. the same.

The function of the front oxygen sensor is mainly feedback. In short, it is to detect the oxygen content in the exhaust gas produced by the combustion of the cylinder mixture. Generally, a high oxygen content indicates that the mixture is lean, and a low oxygen content indicates that the mixture is too rich. The difference in the content transmits different electrical signals to the ECU, so that the ECU can correct the mixture according to this information.

The function of the rear oxygen sensor is mainly to check the purification effect of the three-way catalysis, that is, to detect the oxygen content in the exhaust gas after purification, and feed it back to the ECU, and the computer will compare the data of the front oxygen supply. If the data output is the same (generally the front oxygen signal is greater than the rear oxygen), then it can be judged that the three-way catalysis is invalid, and the fault light of the engine will light up at this time, reminding the owner to repair the three-way catalysis.

Oxygen sensor common faults

Poisoning fault

Oxygen sensor poisoning includes lead poisoning and silicon poisoning. The former is often seen in cars using leaded gasoline, and the latter is a silicon dioxide substance produced by the combustion of silicon compounds contained in gasoline and lubricants. If it is only mildly poisoned, cleaning can be done, but once the internal structure of the oxygen sensor is damaged, it must be replaced directly.

Ceramic chipping

The ceramic of the oxygen sensor is hard and brittle, and it may be broken and invalidated by hitting it with a hard object or blowing it with a strong airflow. Therefore, special care should be taken when handling, and replacements should be made in time if problems are found.

The wire is blown

The heater resistance wire is burned out. For the heating type 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.

Line disconnection

The internal circuit of the oxygen sensor is disconnected.

Observe the top part of the oxygen sensor to determine the fault:

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

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

3. Brown tip (as shown in the picture): caused by lead pollution, if it is serious, the oxygen sensor must also be replaced;

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

To measure the resistance of the oxygen sensor:

Unplug the sensor plug and measure the resistance of two of the wires to see if it is in a suitable range (usually about 3 or 5 ohms), which is normal.

Post time: Apr-23-2022