Lambda probe: causes of malfunction. Possible signs of a malfunctioning oxygen sensor. Oxygen sensor: replacement, check, malfunctions The lambda probe is covered, what to do

The purpose of the lambda probe (oxygen sensor) is to transmit information about the composition of the working mixture from the exhaust manifold to the ECU. The combustion quality of the fuel-air mixture (FA) directly affects engine performance.

Modern cars with injection engines are equipped with one or more catalysts and two or more oxygen sensors. Where is the lambda probe located? Depends on the type of car. Common systems include two devices, located before and after the catalyst. In this way, the excess oxygen in the mixture is determined before gases enter the device. In cars with one probe - installed at the front, on the exhaust manifold.

How does an oxygen sensor work?

The ECU measures the amount of fuel supplied using injectors, setting the volume at a certain moment. The probe provides feedback, which allows you to accurately determine the proportions of gasoline, diesel or gas. The ECU requests information once every 0.5 seconds at idle. At higher speeds, the frequency of requests increases proportionally. Analyzing the data, the control unit adjusts the composition of the fuel assembly, making it poorer or richer. Maintaining optimal fuel assembly is the purpose of lambda probes. The ideal air to fuel ratio is 14.7:1 (gasoline), 15.5:1 (gas) and 14.6:1 (diesel).

• Point-to-point, narrowband (simple). It works based on measuring the amount of oxygen in the exhaust gases. The poorer the fuel assembly, the lower the voltage; the richer, the higher.

Average lifespan of oxygen sensors Russian gasoline 40,000-100,000 km. To increase service life, it is recommended to fill quality fuel with low content of impurities and heavy metals. It is quite difficult to determine a malfunction by self-diagnosis, and it is almost impossible to establish the cause. This may be wear and tear, low quality gasoline, mechanical damage and other factors.

• Short circuit in the wiring;
• Misfires;
• Natural wear and tear. In conditions of low-quality fuel, the average service life of the sensor is 40-70 thousand km.

• Fuel consumption increases. Every motorist monitors the fullness of the tank and tries to find his cruising speed when flow is minimal. Therefore, increased fuel consumption will be noticed immediately. Depending on the severity of the lambda probe malfunction, it increases by 1-4 liters. Increased consumption, of course, can cause not only a faulty oxygen sensor.

How to check a lambda probe

The procedure is as follows:

1. Test the probe signal using a motor tester, a dial voltmeter or an oscilloscope. Connect the tester between the ground wire and the signal wire, raise the speed to 3,000 Nm, note the time and monitor the readings. They should vary from 0.1 to 0.9 volts. We recommend replacing the sensor if the range of changes is less or less than 9-10 readings have changed in 10 seconds. The cause of the error may be “fatigue” and slow response of the system.

Video instruction:

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The purpose of the lambda probe (oxygen sensor) is to transmit information about the composition of the working mixture from the exhaust manifold to the ECU. The combustion quality of the fuel-air mixture (FA) directly affects engine performance.

Correct operation of the oxygen sensor helps:

• Increase engine performance by determining a close-to-ideal proportion of injected fuel and air.
• Reduce the production of harmful gases (CO, CH, NOx) emitted into the atmosphere and establish economical operation of the vehicle due to the correctly selected composition of the working mixture.

Modern cars with injection engines are equipped with one or more catalysts and two or more oxygen sensors. Where is the lambda probe located? Depends on the type of car. Common systems include two devices, located before and after the catalyst. In this way, the excess oxygen in the mixture is determined before gases enter the device. In cars with one probe - installed at the front, on the exhaust manifold.

How does an oxygen sensor work?

The ECU measures the amount of fuel supplied using injectors, setting the volume at a certain moment. The probe provides feedback, which allows you to accurately determine the proportions of gasoline, diesel or gas. The ECU requests information once every 0.5 seconds at idle. At higher speeds, the frequency of requests increases proportionally. Analyzing the data, the control unit adjusts the composition of the fuel assembly, making it poorer or richer. Maintaining optimal fuel assembly is the purpose of lambda probes. The ideal air to fuel ratio is 14.7:1 (gasoline), 15.5:1 (gas) and 14.6:1 (diesel).

Types of oxygen sensors according to their design and operating principle:

• Point-to-point, narrowband (simple). It works based on measuring the amount of oxygen in the exhaust gases. The poorer the fuel assembly, the lower the voltage, the richer the higher.
• Broadband. Generates a wider range signal for accurate estimation of proportions in fuel assemblies.

The average lifespan of oxygen sensors using Russian gasoline is 40,000–100,000 km. To increase service life, it is recommended to fill with high-quality fuel with a low content of impurities and heavy metals. It is quite difficult to determine a malfunction by self-diagnosis, and it is almost impossible to establish the cause. This may be wear and tear, low quality gasoline, mechanical damage and other factors.

If you suspect a faulty oxygen sensor, contact a professional diagnostician. Using an oscillogram, a specialist will determine the causes of the malfunction and suggest solutions.

What causes a lambda probe to fail?

• Mechanical damage. A strong impact as a result of an accident, hitting a curb or driving off-road negatively affects the condition of the probe;
• Incorrect engine operation and malfunctions of the ignition system lead to overheating of the oxygen sensor and failure;
• System clogged. The main cause of malfunction of the lambda probe will be combustion products of low-quality fuel. The more heavy metals, the sooner it will clog;
• Breakdown in piston group. A faulty piston, piston pin and connecting rod are leaking oil into exhaust system, which clogs the probe;
• Liquid ingress. Contamination of any kind will shorten the life of the probe;
• Short circuit in the wiring;
• Too rich or lean air/fuel mixture;
• Depressurization of the exhaust system allows air and exhaust gases to pass through, which disables the lambda probe;
• Misfires;
• Fuel additives and improvers;
• Natural wear and tear. In conditions of low-quality fuel, the average service life of the sensor is 40–70 thousand km.

The failure of the lambda probe occurs gradually. The consequences of a faulty oxygen sensor result in emergency engine control mode. This is how manufacturers protect the car from serious damage, and the driver from emergency situations.

Signs of a malfunctioning lambda probe

• The level of gas toxicity increases. Toxicity can be determined using diagnostics. There is no way to diagnose it externally, even the smell of the exhaust will remain virtually unchanged.
• Fuel consumption increases. Every motorist monitors the fullness of the tank and tries to find his cruising speed when consumption is minimal. Therefore, increased fuel consumption will be noticed immediately. Depending on the severity of the lambda probe malfunction, it increases by 1–4 liters. Increased consumption, of course, can be caused not only by a faulty oxygen sensor.
• Oxygen sensor errors are displayed (P0131, P0135, P0141 and others), “ Check Engine" Typically, a check appears when the probes or catalyst are faulty. Diagnostics will determine the exact cause.
• The catalyst is overheating. Faulty lambda probes send incorrect signals to the ECU, which can lead to incorrect operation of the catalyst, its overheating to the point of being hot, and subsequent failure.
• Jerking and uncharacteristic popping noises appear in the engine. Lambda probes stop generating the correct signal, which causes the speed to destabilize idle move. RPM fluctuates over a wide range, which leads to deterioration in quality fuel mixture.
• Are getting worse dynamic characteristics car, power and traction are lost. Similar signs appear in advanced situations. Faulty sensors They also stop working when the engine is not warmed up, and the car signals problems in the system in various ways.

If you are concerned about any of these signs, consult a specialist. Using diagnostic equipment, he will determine the exact area of ​​\u200b\u200bthe breakdown and help in correcting it.

How to check a lambda probe

So, the car drives jerkily, fuel consumption has increased, and the Check Engine light comes on. The symptoms are not typical only for a lambda failure, so a complete diagnosis of the systems is needed. But if you are sure that this is the problem, we will tell you how to check the sensor yourself.

The procedure is as follows:

1. Warm up the engine until operating temperature. An unheated lambda probe will not work.
2. Remove and inspect the probe and wiring for mechanical damage and contamination. If it is bent, scratched, or covered in soot, lead, or white or gray residue, replace it.
3. Check the functionality of the lambda probe with an ohmmeter. Often the cause of the malfunction lies in the breakdown of the heating coil or wires to it. How to “ring” him? Connect an ohmmeter between the heater wires, previously disconnected from the block. When operating properly, the signal circuit resistance is different cars varies from 2 to 10 Ohms and from 1 kOhm to 10 mOhm in the heating circuit. If it is not there at all, there is a break in the wiring.
4. Test the probe signal using a motor tester, a dial voltmeter or an oscilloscope. Connect the tester between the ground wire and the signal wire, raise the speed to 3,000 Nm, note the time and monitor the readings. They should vary from 0.1 to 0.9 volts. We recommend replacing the sensor if the range of changes is smaller or less than 9–10 readings change in 10 seconds. The cause of the error may be “fatigue” and slow response of the system.
5. Check the functionality of the lambda probe using the reference voltage. Start the car, measure the voltage between ground and signal wire. If the readings differ from 0.45 volts by more than 0.2, the sensor or the circuits in the circuit leading to it are faulty.

If there are no instruments to check the functionality of the lambda probe, contact a specialist. They will carry out a full diagnostic and accurately identify the cause of the malfunction for less money and time that you would spend on purchasing devices and identifying the malfunction yourself.

Video instruction:

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Considered more economical and much more user friendly environment. Moreover, the power supply system of such an internal combustion engine has a large number of sensors.

The lambda probe (oxygen sensor) is an important element of the power system injection engines. Moreover, this sensor is no different for a long time services for a number of reasons.

If the lambda probe fails, the engine may operate unstably, lose power, etc. Next, we will look at what a lambda sensor is in a car, the main purpose of a lambda in a car, what signs indicate problems with this element, and also how to check the oxygen sensor

Read in this article

Oxygen sensor in a car: purpose and principle of operation

The main task of engine sensors is to transmit signals, many of which allow the control unit to flexibly adjust the fuel-air mixture taking into account constantly changing operating conditions and loads on the internal combustion engine.

In turn, it is difficult to overestimate the importance of the lambda probe (sometimes car enthusiasts on forums mistakenly call this element lambda probe or lambdazone). Simply put, oxygen sensors in a car measure the excess air ratio in the air-fuel mixture.

The general design of the lambda probe is as follows:

• metal body;
• ceramic insulator;
• sealing ring;
• wiring and cuffs for sealing;
• protective housing with a hole for ventilation);
• conductive contact;
• ceramic tip;
• spiral in the tank;
• protective shield with a hole for releasing gases.

For the production of sensors of this type Heat-resistant materials are needed since the device operates at high temperatures. In total, oxygen sensors are divided into several types, depending on the number of wires per sensor.

In fact, this sensor determines the excess air ratio by “sniffing” the exhaust and detecting residual oxygen in the exhaust gases. The main task of the oxygen sensor is to transmit to the engine ECU important information, which allows the controller to determine how efficiently the fuel combustion process occurs in the cylinders.

This information is needed in order to maintain optimal conditions for the operation of the catalyst (catalytic converter), which filters vehicle exhaust and reduces the amount of harmful emissions into the atmosphere.

The main reason for such control is that the most efficient operation of the catalyst is possible only when 14.6–14.8 parts of air and 1 part of fuel are burned in the engine. When such a mixture burns, lambda will be equal to 1 ± 0.01.

It is quite obvious that in order to constantly prepare such a mixture in different modes, you need a developed power system with electronic fuel injection, which constantly receives signals from sensors (including the oxygen sensor).

At the same time, the lambda probe itself is in exhaust system, operates in high heat conditions, and may also fail if there are faults in the motor. Let's look at the signs and causes of lambda failures.

Lambda probe: signs of malfunction

As a rule, the oxygen sensor (lambda probe) may fail or work intermittently if the engine itself is worn out or faulty.

For example, if not working properly, it gets into the cylinders and then into the exhaust. engine oil. It can also get into the cylinders, etc. All this leads to the fact that the sensor resource is reduced or the element stops working.

Problems with mixture formation or ignition, overheating, short circuits and faulty wiring, and contamination of the sensor (including after combustion of gasoline with a high content of additives to increase the octane number) can also damage the lambda.

One way or another, in the case of faulty lambda- probe, the CO content in the exhaust gases increases from 0.1–0.3% to 4–6% or more. In this case, usually:

• the engine loses power;
• the engine jerks, the speed fluctuates;
• fuel consumption increases;
• the check light is on on the instrument panel;
• The internal combustion engine may operate unstably, in emergency mode etc.

By the way, some cars may only have one such sensor, while others may have a second lambda probe, and there may be more sensors. In the first case, the lambda can often be disabled programmatically.

On cars with two lambda probes, especially if the second oxygen sensor fails, solving the problem is much more difficult. The fact is that you will need to actively interfere with the operation of electronic systems, reflash the ECU, install so-called lambda probe decoys, etc.

How to check the lambda, repair or replace the oxygen sensor

• Most effective way check is a computer diagnostics of the engine, which allows you to determine errors using the lambda probe. Decoding errors computer diagnostics engine allows you to localize the problem.
• You can also install a known working sensor on your car. Afterwards you need to reset the errors. If engine operation returns to normal, then the cause is the oxygen sensor.
• The performance of the lambda probe can also be assessed visually. This visual check will not be accurate, but is sometimes effective. To begin with, inspect the wire connectors. Everything must be in place and securely fastened.

Then you can unscrew and inspect the oxygen sensor. If soot is visible (most often resulting from problems with the lambda probe heater or after combustion of a rich mixture), the dirty sensor loses its ability to properly assess the composition of the exhaust.

The problem will also be indicated by the presence of shiny deposits. gray, which indicate an excess of lead in the fuel. Typically, lead leads to failure of the sensor and often the catalyst. If there are visible whitish deposits, this is also a bad indicator. In this case, the lambda can be “killed” by additives in the fuel or engine oil.

• Another way to check is to test the lambda with a voltmeter tester. To quickly check the lambda probe, the tester is switched to constant voltage measurement mode. The car is started by disconnecting the oxygen sensor from the block before starting. Next, its signal wire is connected to a voltmeter.

Then you will need to raise the engine speed to 2.5 thousand rpm and release the gas pedal. Then you need to remove the vacuum tube from the fuel pressure regulator. After this, you can evaluate the tester readings. If diagnostics and testing of the lambda probe shows 0.8V or less, or there is no reading at all, then it is clear that the lambda probe is faulty.

The test must also be repeated by creating a lean mixture. To do this, you need to suck air through the vacuum tube. If the oxygen sensor is working properly, then the voltmeter reading will be 0.2 V or less.

If all checks show that the sensor is faulty, then the lambda probe needs to be replaced. Also, in some cases, cleaning can help, but this method is not always effective.

How to clean a lambda probe

Let us note right away that the part is officially non-repairable, that is, the lambda probe is not supposed to be repaired and the sensor needs to be replaced. However, often the element fails precisely because of carbon deposits on the sensitive element. This element is under a protective cap.

It is quite obvious that if you remove the carbon deposits, there is a chance that the sensor will work. As a rule, you can try to clean the lambda in orthophosphoric acid. This acid removes soot and dirt in 20-30 minutes without causing harm to sensitive electrodes.

The difficulty is that you can effectively clean the oxygen sensor by removing the protective cap. If external washing does not help, the cap is removed on a lathe. Next, after cleaning, the cap must be re-attached. It is usually secured using argon welding. If such cleaning does not produce results, the only solution is to replace the lambda sensor.

Replacing the oxygen sensor

Let's start with the fact that if the car has a heated oxygen sensor, it can often be replaced with an unheated lambda probe. You can also make a reverse replacement with a heated part. Even if the electrical circuit connectors do not match, you can use universal contacts.

As for the replacement itself, you need to change the oxygen sensor only after the engine has cooled down. The lambda probe must be replaced after the ignition is turned off. It is optimal to buy a lambda probe that has a marking similar to that of the element installed on the car.

The replacement itself is performed as follows:

• First you need to disconnect the wires from the sensor;
• then the lambda probe is unscrewed with a wrench;
• then a new element is screwed in and the wiring is connected;
• the final stage is checking the functionality of the sensor;

Please note that when unscrewing and tightening the lambda probe, it is important not to break the thread, that is, you should not use unnecessary force.

As you can see, diagnosing lambda problems requires separate knowledge of what signs indicate malfunctions of the oxygen sensor, as well as how to check the lambda probe with a voltmeter.

By the way, it is recommended to check the lambda probe every 30-40 thousand km. mileage, especially if there are problems with mixture formation. To check, you need to warm up the engine, then raise the idle speed to 2 thousand rpm. On the voltmeter, the lambda probe voltage should be between 0 and 1 V (taking into account the exhaust temperature of 300–400 degrees Celsius).

Please note that it is under heating conditions that the zirconium electrode becomes able to conduct current, and the amount of oxygen in the atmosphere and oxygen in the exhaust causes an output voltage to appear on the electrodes of the lambda probe. It is for this reason that the lambda probe is checked on a well-warmed engine.

We also note that if there is such a possibility, it is better to use an oscilloscope rather than a multimeter to check. It is the first option that allows you to more accurately assess the signal quality. You also need to measure the resistance of the sensor heater. Measurements are first taken with the plug removed, the norm at normal temperatures is 2 -14 Ohms.

Then the voltage on the heater is measured (with the ignition on and the sensor connector connected). Normally, the indicator should be at least 10.5 V. If the value is less, the wiring, contacts, etc. are checked.

It should also be noted that in the case where the lambda probe was previously unscrewed and put back, it is recommended to treat the threads with a special mounting paste. However, such paste should not be allowed to come into contact with the protective tube in order to avoid contamination and possible malfunctions of the sensor.

If the device is new, large manufacturers Sensors treated with paste are already supplied from the factory. The main thing is to observe the recommended tightening torque when installing the lambda probe (usually 40, 50 or 60 Nm).

Finally, we note that the lambda probe is a very fragile and sensitive sensor. It must be carefully screwed in, not dropped during installation, it must not be knocked on the oxygen sensor, it must not become oily or dirty, etc.

Considering that the sensor takes outside air for comparison with the exhaust, and the intake occurs through the connecting connector, such a connector cannot be filled with contact sprays or lubricated.

Particular care should be taken when... The lambda probe connector must be separately and properly insulated. Even when driving off-road, the sensor can be mechanically damaged or contaminated. To avoid this, you should take into account the features and location of its installation on the machine. As a rule, it allows you to partially protect the lambda.

What's the result?

As you can see, the oxygen sensor in a car is an important element on which the quality and composition of the fuel-air mixture directly depends. At the same time, the lambda probe does not have a long service life and can fail for a number of reasons. One way or another, this element needs to be checked and replaced if necessary.

As a summary, we note that operating a car with a faulty lambda probe is strongly not recommended. The fact is that problems with the oxygen sensor can cause failure of the catalyst, which is a much more expensive element than the oxygen sensor.

Foreign cars produced since the 80s already had a lambda probe in their design in European or American models. It participates in the chain of formation of the fuel mixture. The sensor contributes to the balance of its formation. To a good driver It is worth knowing the signs of a faulty lambda probe, since the performance of the car depends on its condition.

How does the sensor work?

The basic task performed by the λ probe is to control the volume fraction of oxygen in each portion exhaust gases. The optimal value should be within the range of 0.15–0.3%. A significant deviation from the norm specified by the manufacturer leads to negative consequences with power plant vehicle.

Traditionally, the oxygen sensor is installed in the exhaust manifold near the connecting pipes. Less often, in some models, designers place it in a different place. However, the position does not affect performance.

There are variations of oxygen sensors of both broadband type and two-channel type. In the first case, the device is described from high- and middle-class cars, and in the second - from economy cars and vehicles produced 2-3 decades ago. Also characteristic of progressive designs is the balancing of the correct indication and a high degree of accuracy.

It is important to know that due to the hard work of oxygen sensors in cars, the service life of engines is significantly increased, the speed is balanced and fuel consumption is reduced.

Due to their design features and a certain location in the collector, a uniform signal is not expected from the sensor. This is influenced by the fact that the controlled exhaust gases are monitored after a large number of operating cycles. In fact, the λ-probe is able to react after the fact to failures and send information about this to the ECU.

Signs of a malfunctioning oxygen sensor

Malfunctions of the device affect the operation of the motor as a whole. Failure can unbalance smooth functioning fuel system, sending a mixture calculated by proportions into the combustion chamber.

The following symptoms appear:

• outside air and exhausts penetrate inside;
• the housing becomes depressurized;
• the device becomes obsolete;
• the oxygen sensor overheats due to improper operation of the ignition;
• there are problems with the electrical wiring, which affects the quality of the signal sent to the electronic control unit;
• mechanical damage occurred due to improper operation of the vehicle.

Usually, external consequences begin to appear gradually, so car enthusiasts do not always correlate the troubles of the ignition system with the lambda probe. Although detecting it and monitoring its condition will not be difficult.

At first, fluctuations in performance occur over a wide range. The quality of the fuel mixture deteriorates periodically.

Drivers should know how the car behaves if the lambda probe does not work. There are unreasonable jerks in operation, uncharacteristic popping sounds from the engine or closer to the exhaust. Often, a characteristic light indicator lights up on the dashboard while driving. Such anomalies should not be ignored, but it is worth conducting an initial diagnosis.

It is important to check the sensor if there is a significant decrease in power. This is especially true for cases where there are no obvious reasons for this. You will need to look into the unit when the car stops reacting quickly to pressing the gas pedal, and at the same time you hear popping noises from the engine compartment. Noticeable overheating of the engine should not be overlooked.

Manufacturers of modern cars can start signals on dashboard, as well as completely blocking the movement of the machine. The driver will only have to call an emergency evacuation.

The most problematic type of failure is considered to be loss of sensor tightness. We do not recommend continuing to drive in this case, as it can lead to more serious engine damage. With such a flaw, the gases from the exhaust are not sent into the pipe, but are able to penetrate into the area where the reference atmospheric air is located. Thus, the sensor detects an excess of molecules and sends incorrect signals to the computer, disabling it.

Loss of power is a sure sign of decreased tightness of the lambda probe. The engine also starts knocking and there is a smell of exhaust in the cabin. You can notice the symptoms by an increase in carbon deposits on the exhaust valves and around the spark plugs.

The device will have to be tested or completely changed. In a service station, expensive oscilloscopes are used, and in a home garage, multimeters are used for this. Based on the test results, the final decision is made on what to do with the sensor.

As a rule, most motorists do not carry out repairs on oxygen sensors. They are simply changed or a special homemade plug is installed. It is preferable to carry out final diagnostics using high-quality equipment to make sure that it is the lambda probe that needs to be repaired.

Most cars produced since the late 70s - early 80s are equipped with catalytic exhaust gas converters (colloquially -), which can significantly reduce the toxicity of waste materials, reducing the damage caused to the environment. Enough interesting fact is that the catalyst can maintain functionality only under conditions of ideal mixture formation, in which 1 part of fuel contains from 14.6 to 14.8 parts of atmospheric air with a normal oxygen content. To prevent the mixture from being over-enriched or over-lean, it is necessary to use electronic control fuel supply - in such a system, the quality of the combustible composition is controlled by a lambda probe. Despite its location in an aggressive environment, this device is quite fragile and unstable, and is subject to frequent damage. If the lambda probe in your car has stopped working, signs of a malfunction can be detected without specialized equipment - it is impossible to continue operating the vehicle.

Mechanism of action

The lambda probe detects chemical composition by searching for oxygen in them and determining the percentage. In the normal state of the mixture, this figure is 0.1–0.3% - small fluctuations are allowed due to the fact that the fuel supply mode to the engine cannot be stable over a significant period of time. The lambda probe is installed directly into the exhaust manifold - usually its installation is carried out at the junction of the pipes extending from various cylinders (in common parlance - “pants”), although there are other options.

There are various modifications of lambda probes - and also in vehicles of previous years of production, the devices have a two-channel layout. They can only determine the presence of a deviation in oxygen content to positive or negative side, which is accompanied by a change in the voltage of the electrical signal transmitted to the electronic unit. However, all modern cars of the middle and elite classes are already equipped with broadband-type lambda probes, which are already designed to determine the percentage deviation of the content of the required element from the norm. Thanks to this, a significant improvement in engine performance is achieved:

• Stability of speed retention increases;
• Fuel costs are reduced;
• The resource of the vehicle increases.

If you are interested in the electrical engineering side of the lambda probe, then it is worth mentioning that this device cannot generate a uniform signal. Due to the fact that the standard lambda probe is located in the exhaust manifold, when the exhaust gas reaches its location, several operating cycles may already have passed. In this case, the quality of mixture formation deteriorates by 3–5%, which is accompanied by some destabilization of the engine. The lambda probe reacts to this by changing the voltage supplied to the central injection control unit, which takes the necessary measures.

Determining the breakdown

External signs

If the lambda probe malfunctions, there is a significant deterioration in the quality of the fuel mixture, which is externally expressed in deterioration in engine performance. It is worth saying that there can be many - among them the following main ones can be distinguished:

• Depressurization of the sensor housing, penetration of atmospheric air and exhaust gases;
• Overheating of the lambda probe as a result of inept engine tuning;
• Failure as a result of prolonged exposure to an aggressive environment (aging);
• Blocking of the working surface of the lambda probe with combustion products of low-quality fuel;
• Disturbances in the normal power supply and interruption of the line leading to the control unit;
• Strong blow to the lambda probe housing with destruction internal components, for example, when actively driving on bad roads.

In all cases, except for mechanical damage accompanied by depressurization, malfunctions of the lambda probe appear gradually, with stepwise deterioration. Another exception is a broken wiring - however, it cannot be considered a malfunction of the lambda probe itself, so it should be considered in a separate topic for discussion. For everyone else, the following stages of malfunction development can be distinguished.

Video on how to check the lambda probe:

Initially, the device ceases to normally perform its functions in extreme operating conditions of the engine, when its electrical characteristics have already deteriorated so much that the sensor cannot generate. A malfunction of the lambda probe manifests itself in destabilization of the idle speed, which begins to “float” in a fairly wide range, the length of which is 300–600 rpm. Upon reaching very high speed, not belonging to the critical level, a sharp change in the quality of the fuel mixture may occur. In this case, the car may twitch strongly, in some cases abrupt popping sounds can be heard from under the hood, and the warning lamp, signaling abnormal engine operation. When the speed decreases, all signs of a lambda probe failure disappear, but they cannot be ignored.

At the second stage, the device stops working on a cold engine - until the temperature reaches the maximum possible, the car will show all signs of malfunction intake system or gas distribution mechanism. In particular, you will notice a significant reduction in power, extremely slow responses to changes in the position of the gas pedal, and jerking and popping. If the lambda probe malfunctions, the car may twitch, slow down sharply as a result of a complete stop in the fuel supply, and... After about 5–10 minutes of driving in such an unpleasant mode, a visible stabilization of the vehicle’s condition occurs - however, it is exclusively temporary.

If you do not take any measures regarding malfunctions of the lambda probe at the previous stage, the device will completely fail, which will cause many negative consequences. In addition to a significant deterioration in dynamics and the impossibility of normal movement in continuous mode, you will be faced with an increase in fuel consumption by 15–30%, as well as a significant increase in exhaust toxicity, which can be determined by the clearly noticeable tint of fuel. Modern cars can generally block all driver actions when the lambda probe is faulty by switching to emergency mode.

Worst option

If the above-mentioned depressurization of the lambda probe occurs, it is impossible to continue operating the vehicle, as this may lead to complete engine failure followed by expensive repairs. In this phenomenon, exhaust gases enter a duct that is used to draw in atmospheric reference air to compare the two types of gases and determine the optimal oxygen content. If engine braking occurs, atmospheric air with a minimum amount of impurities passes through - therefore, the lambda probe sees that there is much more oxygen in the manifold than in the environment! The result of this is the formation of powerful negative signals that completely disrupt the normal operation of the injection control unit.

Electronic diagnostics

If you want to know what signs of lambda probe failure can be detected during a professional inspection, you should find specialized equipment. When examining a lambda probe, an electronic oscilloscope is used - some experts recommend using a multimeter, but it can only determine the fact that the device has failed. The device is checked with the engine running, heated to a circuit temperature of 80–90 degrees. When cold, the sensor may give readings that deviate significantly from the norm.

There can be many signs of a device malfunction. They are represented by smooth signal characteristics or an increase in level not exceeding 0.1 V. In addition, it is worth paying attention to the shape of the curve - the changes should be quite steep, not allowing a smooth increase in voltage. Experts say that the lambda probe must change the signal level every 120 ms - otherwise it is possible to talk about its malfunction.

Car repair

Almost all manufacturers of vehicles and individual components for them claim that the lambda probe cannot be repaired - it only requires complete replacement node. At the same time, its cost can be very impressive - especially if you own a luxury brand car. A common way out is to purchase a universal sensor equipped with a special adapter for a specific type of vehicle. Such devices are manufactured by Bosch - using its services, you can even purchase used refurbished spare parts, which have a reduced cost and limited duration. In addition, you can buy a used exhaust manifold with a pre-installed lambda probe.

If you are absolutely sure that the lambda probe is not functioning correctly as a result of combustion products deposited on it, you can try it. To do this, the device is dismantled at a surface temperature of 40–50 degrees, the protective cap is removed from it and the contacts are immersed in phosphoric acid. After several washes, the lambda probe is washed with clean water, thoroughly dried and installed in place, not forgetting to lubricate the threads with a special sealing paste. The tightening torque is set by the manufacturer - it usually varies between 40–60 Nm. This procedure helps in 80% of cases of the described malfunctions.

The main thing is timely diagnosis

If you discover in time that the car’s malfunction lies precisely in the breakdown of the standard lambda probe, you will be able to carry out the necessary repairs even before the consequences affect the engine, leading to its significant breakdown. In addition, by eliminating such a problem, you will be able to maintain the most important characteristics of the vehicle at the same level, which will help you use it to the fullest and most profitably. It’s up to you to decide which troubleshooting method you choose, but it’s worth remembering that working with car electronics without the appropriate qualifications is very dangerous.

Unfortunately, not all car owners know what a lambda probe is and why it is needed. The lambda probe is an oxygen sensor that allows electronic system control and balance the correct ratio of air and gasoline in the combustion chambers. It is able to promptly correct the structure of the fuel mixture and prevent destabilization of the engine operating process.

This rather fragile device is located in a very aggressive environment, so its operation must be constantly monitored, since if it breaks down, further use of the car is impossible. Periodic checking of the lambda probe will guarantee stable operation of the vehicle.

Operating principle of a lambda probe

The main task of the lambda probe is to determine the chemical composition of exhaust gases and the level of oxygen molecules in them. This figure should range from 0.1 to 0.3 percent. Uncontrolled excess of this standard value can lead to unpleasant consequences.

During a standard car assembly, the lambda probe is mounted in the exhaust manifold in the area where the pipes connect, however, sometimes there are other variations in its installation. In principle, a different arrangement does not affect the operating performance of this device.

Today you can find several variations of the lambda probe: with a two-channel layout and a broadband type. The first type is most often found on older cars produced in the 80s, as well as on new economy class models. Broadband type sensor is inherent modern cars middle and upper class. Such a sensor is capable of not only accurately determining the deviation from the norm of a certain element, but also promptly balancing the correct ratio.

Thanks to the hard work of such sensors, the vehicle's operating life is significantly increased, fuel consumption is reduced and the stability of idle speed is increased.

From an electrical engineering point of view, it is worth noting that the oxygen sensor is not capable of creating a uniform signal, since this is prevented by its location in collector zone, because in the process of exhaust gases reaching the device, a certain number of operating cycles may pass. Thus, we can say that the lambda probe reacts rather to destabilization of the engine, which it subsequently notifies the central unit about and takes appropriate measures.

The main symptoms of a malfunctioning lambda probe

The main sign of a faulty lambda probe is a change in engine operation, since after its breakdown the quality of the fuel mixture supplied to the combustion chamber significantly deteriorates. The fuel mixture essentially remains uncontrolled, which is unacceptable.

The reason for the lambda probe to fail to operate may be the following:

• depressurization of the housing;
• penetration of external air and exhaust gases;
• overheating of the sensor due to poor-quality engine painting or improper operation of the ignition system;
• obsolescence;
• incorrect or interrupted power supply that leads to the main control unit;
• mechanical damage due to incorrect operation of the vehicle.

In all of the above cases, except the last one, failure occurs gradually. Therefore, those car owners who do not know how to check the lambda probe and where it is located will most likely not immediately notice the malfunction. However, for experienced drivers Determining the reason for changes in engine performance will not be difficult.

The gradual failure of the lambda probe can be divided into several stages. At the initial stage, the sensor stops functioning normally, that is, at certain operating moments of the engine, the device stops generating a signal, subsequently destabilizing the idle speed.

In other words, they begin to fluctuate over a fairly wide range, which ultimately leads to a loss of quality of the fuel mixture. At the same time, the car begins to twitch for no reason, you can also hear popping noises uncharacteristic of the engine, and a warning light always lights up on the instrument panel. All these anomalous phenomena signal to the car owner that the lambda probe is not working properly.

At the second stage, the sensor stops working completely when the engine is not warmed up, while the car will signal the driver about the problem in every possible way. In particular, there will be a noticeable loss of power, a slow response when pressing the accelerator pedal and the same popping noises from under the hood, as well as unjustified jerking of the car. However, the most significant and extremely dangerous signal of a lambda probe failure is engine overheating.

If you completely ignore all previous signals indicating a deterioration in the condition of the lambda probe, its breakdown is inevitable, which will cause a large number of problems. First of all, the possibility of natural movement will suffer, fuel consumption will also increase significantly and an unpleasant, pungent odor with a pronounced hint of toxicity will appear from the exhaust pipe. In modern automated cars, in the event of a breakdown of the oxygen sensor, an emergency lock can simply be activated, as a result of which subsequent movement of the car becomes impossible. In such cases, only an emergency call to a tow truck can help.

However, the worst case scenario is depressurization of the sensor, since in this case the movement of the car becomes impossible due to the high probability of engine failure and subsequent expensive repairs. During depressurization, exhaust gases, instead of exiting through exhaust pipe, enter the atmospheric reference air intake channel. During engine braking, the lambda probe begins to detect an excess of oxygen molecules and urgently sends a large number of negative signals, which completely disables the injection control system.

The main sign of sensor depressurization is a loss of power, this is especially felt during high-speed driving, a characteristic knocking sound from under the hood while driving, which is accompanied by unpleasant jerking, and an unpleasant odor that is emitted from the exhaust. Depressurization is also indicated by visible deposits of soot formations on the exhaust valve body and in the area of ​​the spark plugs.

How to determine a faulty lambda probe is described in the video:

Electronic lambda probe test

You can find out about the condition of the lambda probe by checking it on professional equipment. An electronic oscilloscope is used for this. Some experts determine the performance of the oxygen sensor using a multimeter, however, it can only state or deny the fact of its failure.

The device is checked during full engine operation, since at rest the sensor will not be able to fully convey a picture of its performance. In case of even a slight deviation from the norm, it is recommended to replace the lambda probe.

Replacing the lambda probe

In most cases, a part such as a lambda probe cannot be repaired, as evidenced by statements about the impossibility of repair from many automobile manufacturers. However, the inflated cost of such a unit is official dealers discourages any desire to acquire it. The optimal way out of this situation could be a universal sensor, which costs much less than its native analogue and is suitable for almost everyone car brands. Also, as an alternative, you can purchase a used sensor, but with a warranty period, or a completely exhaust manifold with a lambda probe installed in it.

However, there are cases when the lambda probe operates with a certain error due to severe contamination as a result of combustion products deposited on it. In order to make sure that this is really the case, the sensor must be checked by specialists. After the lambda probe has been checked and its full functionality has been confirmed, it must be removed, cleaned and reinstalled.

In order to dismantle the oxygen level sensor, it is necessary to warm its surface to 50 degrees. After removal, the protective cap is removed from it and only after that you can start cleaning. It is recommended to use phosphoric acid as a highly effective cleaning agent, which can easily cope with even the most stubborn flammable deposits. At the end of the soaking procedure, the lambda probe is rinsed in clean water, thoroughly dried and installed in place. At the same time, do not forget about lubricating the threads with a special sealant, which will ensure complete tightness.

It is very complex, so it needs constant maintenance and timely preventive maintenance. Therefore, if there is a suspicion that the lambda probe is faulty, it is necessary to immediately diagnose its performance and, if the fact of failure is confirmed, replace the lambda probe. So everything essential functions the vehicle will be maintained at the same level, which will guarantee the absence of further problems with the engine and other important elements of the car.