Is the fault of automobile oxygen sensor renewed or cleaned?

Once a fault occurs, the computer of the electronic fuel injection system will not be able to get the information of oxygen concentration in the exhaust pipe, so it will not be able to feedback control the air-fuel ratio, which will increase the fuel consumption and exhaust pollution of the engine, and the engine will have unstable idle speed, fire and surge. Therefore, it is necessary to troubleshoot or replace it in time. Oxygen sensor poisoning is a common and difficult fault to prevent, especially for cars that often use leaded gasoline. Even the new oxygen sensor can only work for thousands of kilometers. If it is only mild lead poisoning, a case of unleaded gasoline can eliminate the lead on the surface of the oxygen sensor and return to normal work. However, due to the high exhaust temperature, lead often invades its interior, which hinders the diffusion of oxygen ions and makes the oxygen sensor ineffective. At this time, it can only be replaced.

In addition, it is common for oxygen sensors to suffer from silicon poisoning. Generally speaking, the silicon dioxide produced by the combustion of silicon compounds contained in gasoline and lubricating oil, and the silicon gas emitted by improper use of silicone rubber gasket will make the oxygen sensor ineffective, so high-quality fuel oil and lubricating oil must be used.

When repairing, rubber gaskets should be selected and installed correctly, and solvents and anti-sticking agents other than those specified by the manufacturer should not be coated on the sensor. 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 and dust enter the oxygen sensor, which will hinder or prevent the outside air from entering the oxygen sensor, making the output signal of the oxygen sensor inaccurate and the ECU unable to 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. When measuring the feedback voltage of the oxygen sensor, unplug the wiring harness plug of the oxygen sensor, lead a thin wire from the feedback voltage output end of the oxygen sensor according to the vehicle circuit diagram, then plug in the wiring harness plug, and measure the feedback voltage from the lead when the engine is running (some vehicles can also measure the feedback voltage of the oxygen sensor from the fault detection socket, for example, a series of cars produced by Toyota Motor Corporation can directly measure the feedback voltage of the oxygen sensor from the OX 1 or OX2 terminal in the fault detection socket.

When detecting the feedback voltage of oxygen sensor, it is best to use pointer multimeter with low range (generally 2V) and high impedance (internal resistance greater than10mΩ). The specific detection method is as follows:

1. Preheat the engine to normal operating temperature (or run it at 2500 rpm for 2 minutes after starting);

2. Connect the negative probe of voltage range of multimeter to the negative electrode of E 1 or battery of fault detection socket, and connect the positive probe to the OX 1 or OX2 jack of fault detection socket, or connect the No. | Socket on the oxygen sensor harness plug;

3. Keep the engine running at about 2500 rpm, check whether the voltmeter pointer can swing back and forth between 0- 1V, and record the number of times the voltmeter pointer swings within 10s. Under normal circumstances, with the progress of feedback control, the feedback voltage of the oxygen sensor will constantly change around 0.45V, and the number of changes of the feedback voltage within 10s should be no less than 8 times.

If it is less than 8 times, it means that the oxygen sensor or feedback control system is not working normally, which may be due to the carbon on the surface of the oxygen sensor, which reduces the sensitivity. Therefore, the engine should run at 2500 rpm for about 2 minutes to remove carbon deposits on the surface of the oxygen sensor, and then check the feedback voltage. If the voltmeter pointer changes slowly after removing the carbon deposit, it means that the oxygen sensor is damaged or the computer feedback control circuit is faulty.

4. Check whether the oxygen sensor is damaged.

Unplug the harness plug of the oxygen sensor, so that the oxygen sensor is no longer connected to the computer, and the feedback control system is in an open-loop control state. Connect the positive probe of the multimeter voltage range directly to the feedback voltage output end of the oxygen sensor, and the negative probe is well grounded. When measuring the feedback voltage during the engine operation, first disconnect the crankcase forced ventilation pipe or other vacuum hoses connected to the intake pipe to artificially form a diluted mixture. At the same time, observe the voltmeter, and the pointer reading should drop.

Then connect the disconnected pipeline, unplug the connector of the water temperature sensor, and replace the water temperature sensor with a 4-8kΩ resistor to artificially form a rich mixture. At the same time, observe the voltmeter, and its pointer reading should rise. You can also change the concentration of mixed gas by suddenly stepping on or releasing the accelerator pedal. When the accelerator pedal is slammed, the mixture will become thicker and the feedback voltage will increase. When the accelerator pedal is suddenly released, the mixture becomes thinner and the feedback voltage should drop. If the feedback voltage of the oxygen sensor does not change as mentioned above, it indicates that the oxygen sensor is damaged.

In addition, when the titanium oxide oxygen sensor is tested by the above method, if it is a good oxygen sensor, the voltage at the output end should fluctuate around 2.5V, otherwise, the sensor can be detached and exposed to the air, and its resistance value can be measured after cooling. If the resistance value is large, the sensor is good, otherwise the sensor should be replaced.

5, oxygen sensor appearance color inspection

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 damaged, replace the oxygen sensor. You can also judge the fault by observing the color of the tip of the oxygen sensor:

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

② White tip: It is caused by silicon pollution, so the oxygen sensor must be replaced;

③ Brown tip (pictured): 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 deposition. After the engine carbon deposit fault is eliminated, the carbon deposit on the oxygen sensor can be automatically removed.