The role of automotive oxygen sensors
Cars usually have two oxygen sensors, one front oxygen and one rear oxygen. The front oxygen is usually installed on the exhaust manifold, and the rear oxygen is installed behind the three-way catalyst. Their respective functions in the exhaust system are not. the same.
The role of the front oxygen sensor is mainly feedback. Simply speaking, it is to detect the oxygen content in the exhaust gas generated after the combustion of the cylinder mixture. Generally, the high oxygen content indicates that the mixture gas is lean, the low oxygen content indicates that the mixture gas is too rich, and the front oxygen sensor is based on oxygen. The difference in content conveys different electrical signals to the ECU so that the ECU can correct the mixture based on this information.
The function of the post-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 compares the data given by the previous oxygen, if the pre-oxygen and the post-oxygen The same data (generally the pre-oxygen signal is greater than the post-oxygen), then you can judge the three-way catalytic failure, at this time the engine's fault light will light up, reminding the owner to overhaul the three-way catalysis.
Oxygen sensor common fault
Oxygen sensor poisoning includes lead poisoning and silicon poisoning. The former is often found in cars that use leaded gasoline, which is a silica material produced by the combustion of silicon compounds contained in gasoline and lubricating oil. If it is only a slight poisoning, it can be cleaned up, but once the internal structure of the oxygen sensor is destroyed, it must be replaced directly.
Oxygen sensor ceramics are hard and brittle, and they can be broken and failed by hard objects or by blowing with a strong air stream. Therefore, be careful when handling and find problems in time.
Resistance wire blown
The heater wire is blown. For the heated oxygen sensor, if the heater wire is ablated, it is difficult to make the sensor reach the normal operating temperature and lose its effect.
The internal line of the oxygen sensor is broken.
Observe the top of the oxygen sensor to determine the fault:
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.
Measure the resistance of the oxygen sensor:
Unplug the sensor and measure the resistance of the two wires to see if they are in the proper range (usually around 3 or 5 ohms).