What Causes An Oxygen Sensor To Fail? (Symptoms and Fixes)

Drivers in the process of operating a car often encounter various breakdowns. Owners of old cars are no longer surprised when the traction suddenly drops or there is a strong consumption of gasoline. But what about beginners who have not yet figured out all the automotive systems? If the above symptoms appear, you should pay attention to the operation of the oxygen sensor it may fail.

Consider all the causes of oxygen sensor to fail and methods for identifying and eliminating them

What Causes An Oxygen Sensor To Fail

Why are o2 sensors called lambda?

The oxygen sensor is also called lambda probe or O2 sensor. Oxygen sensor that evaluates the amount of unburned fuel and oxygen. This device was invented in order to reduce the number of toxic substances in the exhaust. It is the probe that helps to control the amount of O2 in the catalysts.

Many believe that the sensor was invented in order to protect the environment from harmful emissions. On the one hand, this is true, but on the other hand, the device is also installed for the smooth operation of the catalytic converter. The functioning of the catalyst occurs with high efficiency at the moment when the air-fuel mixture has a certain ratio of air and fuel. When the ratio changes, the instrument starts to work inefficiently. This harms the environment.

The composition of the fuel mixture began to be adjusted after the electronic fuel injection systems appeared. Against this background, I had to use “oxygen”. Today, from 1 to several sensors are installed in a car. The second probe began to be used after the introduction of Euro 3 standards.

Before determining the signs of an oxygen sensor malfunction, it is necessary to understand the design of the device. The design includes electrodes and a heating element. Sensors are broadband and two-point. The probe readings are taken into account in the ECU.

Types of oxygen sensor and their improvement

You can determine the visual signs of an oxygen sensor malfunction if you know what type of sensor is installed in the system. Their principle of operation remains the same, but the methods of measuring O2 are different. Manufacturers try to monitor the operation of the probes, and periodically make adjustments to them. This helps to improve the accuracy of the oxygen measurement. For example, tip preheating has recently been introduced. This helped ensure excellent engine idling. The first generation of instruments was heated by the heat of exhaust gases.

The next development was broadband sensors. At first, one sensor was installed in the system, but its indicators were not as accurate as we would like. It was decided to mount a second sensor, which helped to increase the accuracy of measurements. Thus, the broadband type of the sensor works on the basis of the forced injection of oxygen into the chamber.

Today, λ-probes are divided into zirconium, broadband, and titanium. The most common type is zirconia. Titanium is very similar to zirconium visually and technically. As for broadband, they have two cameras, each of which performs its task. Different λ-probes are installed on different cars. To determine the malfunction of the oxygen sensor, you need to know what type it belongs to.

what causes an oxygen sensor to fail and symptoms faulty lambda sensor?

Many drivers do not know what signs of a malfunction of the oxygen sensor are. This question is studied only in direct confrontation with the problem. But as practice shows, if the owner takes care of his car and all its systems, there are no problems with probe malfunctions. Consider when you need to “sound the alarm” and urgently look for a malfunction of the oxygen sensor.

It does not always happen that the oxygenator “broke down in one day” and for no reason. The process occurs gradually and you need to be able to prevent it. If it was not possible to prevent the breakdown, then you can fix it yourself. But first, you should consider the symptoms that indicate the approach to the problem:

  • When the engine is idling, floating speed is observed. If the probe is broken, they change, dropping to values ​​of 400-600. The reason for this is the depletion of the mixture, which is not enough for the normal functioning of the internal combustion engine.
  • A decrease in engine power also occurs due to a lean mixture. The momentum is gaining slowly, and the car cannot drive uphill and accelerates weakly – these symptoms are confirmation of this.
  • High fuel consumption. Consumption increases by at least 30%.
  • Exhaust gases turn black and have a pungent gasoline smell.
  • Candles are covered with a black coating.
  • When accelerating, the car drives jerkily, and not evenly, as expected.

Well, the most obvious symptom is the appearance of an icon on the dashboard. Using a scanner, you can reliably determine that the oxygen sensor is definitely not working, and not another element. The listed signs also include the appearance of a crack in the exhaust pipe area and frequent signals from the computer.

The causes an oxygen sensor to fail that lead to these symptoms are as follows:

  • Low-quality fuel. This is a common reason for drivers who are trying to save on gasoline. Such raw materials contain harmful impurities, and after combustion, they settle on the heating elements. This leads to severe clogging.
  • Wear. It is impossible to avoid natural wear and tear, it always overtakes any element of the car. In this situation, the lambda will have to be replaced.
  • Wiring faults. In order for the probe to connect to the computer, a copper wire is used. Over time, it breaks down or oxidizes, creating problems.

Replacing an oxygen valve is not a routine procedure. But experts still put forward requirements for replacing the sensor. Heated sensors should be replaced every 100 thousand km, and without heating – every 50-80 thousand km. As for planar sensors, they are changed after 160 thousand mileage. Replacement is made after confirmation of the fact of failure. For diagnostics, various instruments are used, including a scanner, a voltmeter, or a multimeter. Repair work takes place in two stages, we will analyze them later.

how does an oxygen sensor go bad? Process

how does an oxygen sensor go bad? Process

As mentioned above, the occurrence of oxygen sensor malfunctions and symptoms is not a quick matter. The occurrence of one of the reasons provokes a gradual failure.

At the initial stage, the oxygenator begins to produce strange symptoms. For example, idle speed deteriorates, signals stop coming, and fuel quality decreases. The driver feels that his car twitches, strange sounds are made, the corresponding icons on the dashboard light up.

If you ignore the problem and do not think about how to troubleshoot the oxygen sensor, then the second stage of the sensor failure process begins. Here the oxygenator completely stops working, all the symptoms of a malfunction become more pronounced. Here it is worth adding a drop in the power of the “engine” and its overheating.

The last stage is the final breakdown of the oxygen sensor. The power of the car will be significantly reduced, a toxic smell will pour out of the pipe. You won’t be able to drive this car. The driver will have to change the part, but a new one (at best), at worst, he will have to undergo a major overhaul.

how to check oxygen sensor?

If the driver felt that the oxygen sensor was not working, the symptoms described above will help to sort out the problem. But here a small dilemma arises. You need to understand whether the sensor has stopped functioning due to a breakdown or if some processes in the system affect its incorrect operation.

For example, if the signal indicates a lean mixture, then you need to understand whether this is really the case. Perhaps there was a depressurization of the exhaust tract. Determining the cause is an important step toward fixing the problem. By the way, there are situations when there are several problems. Let’s say the exhaust manifold sucks and at the same time the fuel pump does not give pressure. Both reasons need to be dealt with.

Many drivers check the oxygen sensor for serviceability using various devices. Most often they use a multimeter or voltmeter. Diagnostics can also be carried out with a diagnostic adapter. Worst case, go to a car dealership. There is also a mechanical check. It involves removing the sensor and inspecting it for soot formation. In this case, cleaning and reinstalling the sensor is required.

is it harmful to drive a car with a bad oxygen sensor?

Having found out what signs of a malfunction the oxygen sensor has, the driver begins to think about how to avoid costly repairs and what consequences the malfunction entails. Firstly, the owner will not be able to start the car in the cold season, since starting will be difficult. The car will start from the second or third time, and in the process of driving it will make different sounds and jerks.

Fuel consumption will also increase significantly, i.e. the more the driver presses the gas pedal, the more gasoline is wasted. In the case of a long drive with a faulty sensor, the catalyst will burn out and the second oxygen sensor will break. With each subsequent launch, there is a strong wear of the compression and piston rings.

The mixture begins to quickly foul the candles. They, in turn, increase resistance. As the chain begins to fail, the wires, the ignition coil. As a result, the driver is waiting for a sad outcome. It is best to replace the sensor at the first stage of failure than to resort to a major overhaul in the future. The cost of the sensor does not exceed 1500 rubles for VAZ cars. The replacement job is not that difficult.

Experts do not advise to pull to the last. It is better to replace the lambda right away than to pay a lot of money for a major overhaul.

how to fix faulty oxygen sensor?

how to fix faulty oxygen sensor?

Repair of the oxygen sensor is carried out in a car repair shop with an experienced specialist. Unfortunately, the spare part should be changed completely, since it simply cannot be repaired. Original sensors have a high cost, so the owners are trying to switch to using universal models. They are suitable for any brand of car and have a low price.

If the problem is not very serious, then you can replace the sensor yourself. For example, if the device becomes dirty, the driver can clean it and insert it back. To dismantle the probe, it is necessary to warm it up to 60°C. After that, you should take out the protective cap and start cleaning. The purification procedure is carried out using phosphoric acid.

At the end of the work, the parts are soaked in water or in a special agent. Only after complete drying, the sensor is put back, having previously lubricated the threads with sealant.

Some drivers think of disabling the probe when problems arise. It is not advisable to do this, since the computer will turn on the offline mixture supply mode. This will lead to the same consequences as ignoring the problem. Disabling the oxygen sensor is not recommended. It is better to replace it with a new one and continue to enjoy your rides.


The article presents materials describing what causes an oxygen sensor to fail, its symptoms, and fixes. There are many reasons why an oxygen valve breaks down. These include wear, low-quality fuel, wiring problems, etc. Do not be indifferent to the problem, as this will lead to negative consequences. It is advisable to replace the sensor with a new one or clean it in case of severe contamination.

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