Common faults and detection methods of the hottest

Common faults and detection methods of oxygen sensor

once the oxygen sensor fails, the computer of the electronic fuel injection system will not be able to get the information of the 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, misfire, surge and other faults. Therefore, the fault must be eliminated or replaced in time

II. Common faults of oxygen sensor:

1. Oxygen sensor poisoning

oxygen sensor poisoning is a frequent and difficult fault to prevent, especially for cars that often use leaded gasoline. Even new oxygen sensors can only work for thousands of kilometers. If there is only slight lead poisoning, then using a box of unleaded gasoline can eliminate the lead on the surface of the oxygen sensor and make it work normally. However, due to the friendly communication and exchange of excessive exhaust temperature, lead invades its interior, hinders the diffusion of oxygen ions, and makes the oxygen sensor ineffective. At this time, it can only be replaced. In addition, silicon poisoning of oxygen sensors is also common. Generally speaking, the silicon dioxide generated after the combustion of silicon compounds contained in gasoline and lubricating oil, and the silicone gas emitted by the improper use of silicone rubber sealing gasket will make the oxygen sensor invalid, so it is necessary to use high-quality fuel and lubricating oil. During repair, the rubber gasket should be selected and installed correctly, and the solvent and anti sticking agent other than those specified by the manufacturer should not be applied to the sensor

2. Carbon deposition

due to the poor combustion of the engine, carbon deposits are formed on the surface of the oxygen sensor, or deposits such as oil or dust enter the oxygen sensor, which will prevent or block the external air from entering the oxygen sensor, making the output signal of the oxygen sensor inaccurate, and ECU cannot correct the air-fuel ratio in time. Carbon deposition is mainly manifested in the increase of fuel consumption and emission concentration. When the maximum pressure is reached, the pressure is relieved. At this time, if the sediment is removed, normal operation will be resumed

3. The oxygen sensor ceramics are broken

the ceramic of the oxygen sensor is hard and brittle. Knocking with a hard object or blowing with strong air flow may break it and fail. Therefore, special care should be taken during handling, and problems should be replaced in time

4. The heater resistance wire is burnt out

for the heated 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

5. The internal circuit of the oxygen sensor is disconnected

III. common faults of oxygen sensor can be detected by the following methods:

1. Check the resistance of oxygen sensor heater. Unplug the harness plug of the oxygen sensor, and measure the resistance between the heater terminal and the grounding terminal in the oxygen sensor terminal with the resistance gear of the multimeter. The resistance value is Ω (refer to the specific model manual). If it does not meet the standard, replace the oxygen sensor

2. Measurement of oxygen sensor feedback voltage. When measuring the feedback voltage of the oxygen sensor, unplug the harness plug of the oxygen sensor, draw a thin wire from the feedback voltage output terminal of the oxygen sensor according to the circuit diagram of the vehicle model, and then insert the harness plug. When the engine is running, Measure the feedback voltage from the outgoing line (for some models, the feedback voltage of the oxygen sensor can also be measured from the fault detection socket. For example, the series cars produced by Toyota Motor Company can directly measure the feedback voltage of the oxygen sensor from the OX1 or ox2 terminal in the fault detection socket). When detecting the feedback voltage of the oxygen sensor, it is best to use a pointer multimeter with low range (usually 2V) and high impedance (internal resistance greater than 10m Ω)

the specific detection methods are as follows: 1) warm up the engine to the normal operating temperature (or run at the speed of 2500r/min for 2min after starting); 2) Connect the negative probe of the multimeter voltage gear to E1 or the negative pole of the battery in the fault detection socket, and the positive probe to OX1 or ox2 Jack in the fault detection socket, or to the No. | outlet on the oxygen sensor harness plug; 3) Keep the engine running at a speed of about 2500r/min, check whether the voltmeter pointer can swing back and forth between V, 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 not be less than 8 times. If it is less than 8 times, it indicates that the oxygen sensor or feedback control system is not working normally, which may be caused by carbon deposition on the surface of the oxygen sensor, which reduces the sensitivity. In this regard, the engine should be operated at a speed of 2500r/min for about 2min to remove carbon deposits on the surface of the oxygen sensor, and then check the feedback voltage. If the voltmeter pointer changes slowly after clearing the carbon deposit, it indicates that the oxygen sensor is damaged or the computer feedback control circuit is faulty. 4) Check the oxygen sensor for damage. Unplug the harness plug of the oxygen sensor, so that the oxygen sensor is no longer connected with the computer, and the feedback control system is in the open-loop control state. Connect the positive probe of the multimeter voltage range directly to the oxygen sensor feedback voltage output terminal, and the negative probe is well grounded. Measure the feedback voltage when the engine is running. First disconnect the positive crankcase ventilation pipe or other vacuum hoses connected to the intake pipe to artificially dilute the mixture. At the same time, watch the voltmeter, and the pointer reading should drop. Then connect the disconnected pipeline, unplug the water temperature sensor connector, replace the water temperature sensor with a K Ω resistance, artificially form a rich mixture, and watch the voltmeter at the same time, and its pointer reading should rise. You can also change the concentration of the mixture by suddenly depressing or releasing the ball screw speed pedal, which is the component driving the sensor movement. When suddenly depressing the accelerator pedal, the mixture becomes thicker and the feedback voltage should rise; When the accelerator pedal was suddenly released, the masonry work of the project was completed in October 2018. The mixture became thinner and the feedback voltage should drop. If the feedback voltage of the oxygen sensor does not change as described above, it indicates that the oxygen sensor has been damaged. In addition, when using the above method to detect titanium oxide oxygen sensor, if it is a good oxygen sensor, the voltage at the output end should fluctuate up and down with 2.5V as the center. Otherwise, the sensor can be removed 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) Check the appearance color of oxygen sensor. Remove the oxygen sensor from the exhaust pipe, and check whether the vent hole on the sensor housing is blocked and whether the ceramic core is damaged. If it is damaged, replace the oxygen sensor. 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 tip: it is caused by silicon pollution. At this time, the oxygen sensor must be replaced; ③ Brown Tip: 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. Generally, the carbon deposition on the oxygen sensor can be removed automatically after the carbon deposition fault of the engine is eliminated