What is the function of lambda probe. Lambda probe (oxygen sensor): How does it work and what is responsible for? Lambda Probe

Lambda probe or oxygen concentration sensor is an element of the exhaust system. It performs the function of determining the volume of oxygen at the outlet of the exhaust system and adjusts the ratio of the components of the fuel and air mixture for the next feed to the combustion chamber of the engine. The constant and uniform feed supply of oxygen and fuel contributes to the correct (both in the field of fuel consumption and in the field of ecology) of the work of the engine.

Location in the system

As already mentioned, the oxygen sensor is placed in the exhaust system. Some machines use 2 probes at once:

• the first lambda probe is in the catalyst;
• the second lambda probe is in the receiving pipe ahead of the catalytic neutralizer.

By type both sensors are similar. They are distinguished only by the fact that in the diagram of the primary longer wire and more holes for removing samples.

Installation and use of 2 probes double the efficiency of tracking concentration and improves the functionality of the catalyst. Each probe has its own heater, and at the same time the resistance of both heaters are not summed up.

Main species

In order to maximize the hydrocarbon and damp gas or decompose nitrogen oxides for oxygen and nitrogen, automotive engineers are invented by 2 types of sensors differing in design.

First type

The 2-crank oxygen sensor can be installed before the catalyst, and after it. It analyzes the number of excess air in oxygen indicators in the development. The Lambda probe this type It is an element of ceramics with a 2-hoody zirconium coating. The measurement process is electrochemically, i.e. Electrodes with one edge have contact with an exhaust gases, and the other with atmospheric.

The functioning of the 2-pointer is based on the measurements of the volume of oxygen, both in the exhaust and in the atmosphere. In the event that the volume of oxygen in the exhaust and in the atmosphere is different, voltage occurs on the edges of the electrode. It turns out that when the value of oxygen volume is greater - a mixture of fuel and air is shifted, and therefore the voltage is reduced. And, on the contrary, the oxygen is smaller, it means that the mixture of fuel and air is enriched, and the voltage increases in proportion.

The most optimal proportion of fuel and air is 14.7 per 1, where 14.7 is a numeric parameter of the air volume required for the combustion of the total fuel.

Second Type

Broadband lambda probe is an improved device. It is used as an input catalyst sensor.

This type of probe contains 2 elements from ceramics - 2-caviction and pumping. Pulling is a physical process, by which oxygen from the exhaust flows through the pumping mechanism under the action of some voltage.

The broadband type function is based on the preservation and support of the same voltage (450 mV) among the electrodes of the 2-sealing mechanism by the necessary correction of the injection voltage.

The reduced value of the volume of oxygen in the development, i.e. When the mixture is enriched, affects the increase in the voltage between the electrodes of the 2-accuracy type of the mechanism. A pulse is transmitted to the control unit, on the basis of which a certain current occurs on the injection mechanism, which promotes injection into the measuring gap, as a result of which the voltage comes to the desired value. The voltage coefficient is a kind of oxygen volume in the exhaust. It is determined using the electronic control unit and, converting, acts on the details in the injection system.

The depleted mixture with the upper oxygen volume limit starts the process of the same type of broadband sensor. The only difference is to turn off the surplus of oxygen from the measuring gap.

The full function of the probe is possible at a temperature of 300 ° C. A faster set of this temperature achieved thanks to special integrated heaters in the form of a spiral. Depending on the car model, each heater has its impedance.

Fault

Lambda probe directly acts on the operation of the motor, because if there is some kind of sensor malfunction, the quality of the fuel and air mixture is rapidly changing, and the motor cannot work as usual. The faulty sensor becomes unpredictable, i.e. Sends various types of signals, often contradicting each other, or at all "does not answer." At such moments, the car stalls or not start.

In order to avoid such consequences, a method that contributes to the launch of the motor and the opportunity to get to the destination was thought out. At the time the sensor fails appear, the control unit activates the emergency operation mode at which the fuel and air supply is performed. Usually at such moments the amount of fuel supplied increases to reduce the likelihood that the car will stall. Obviously, fuel consumption increases, and this is one of the indicators of the breakage of the oxygen device.

In addition to breakdowns of the sensor itself, its functioning may be difficult for a number of other reasons. For example,

• places of fasteners can lose the desired seal;
• the mechanism was initially established incorrectly, i.e. The sensor may not be screwed up to the stop;
• incorrect wire connection makes the item inoperable, which is why the emergency mode will turn on;
• the use of a ethyl type of fuel is able to pretrately pour oxygen and other sensors;
• the overheating of the lambda probe housing (for example, due to damage in the exhaust manifold case).

Ways to independent probe check

Modern oxygen devices may have a single-wire diagram, as well as 2, 3 and 4-wire. The 4-wiring diagram usually has 2 wires that lead to the heating circuit, one - for the flow of signals, and one more - for mass.

1. Analyze the lambda probe for the presence of high or low voltage inside the heating circuit, using any voltmeter. It is necessary to turn on the ignition, then pierce the heater wire for a pointed dipstick or place it into the wire connector. The voltage parameter should be about 12 V. Next, carefully start the motor and, if there is no plus, inspect the circuit from the battery through the fuse and finish the probe itself, and if there is no minus, it is worth checking the circuit to the control unit for the contact loss.
2. To check the resistance of the lambda heater, the probe should be used by an ohmmeter - a tester measuring resistance. First, you need to disconnect the connector and measure the resistance between the heater wires. The lower boundary of the resistance should be at least 2 ohms, and the upper - up to 10 ohm. And when there are no resistance at all, probably the occurrence of the cliff in the device, so it urgently needs its complete replacement.
3. High or low reference voltage is also measured by a voltmeter. Initially, it is necessary to turn on the ignition and measure the voltage between the signal and the mass. This is usually a value \u003d 0.45 V. But when it is greater than or less at 0.2 V and more, this means a malfunction in the signal part of the probe scheme or the contact area with a mass wire is disturbed.
4. The most difficult point is to check the signal of the entire mechanism. There will be an arrow voltmeter or oscilloscope. First of all, you need to start the motor and give it to warm up to earn a lambda probe. Then attach the probe between the wires and the masses. Raise the turnover of the engine approximately up to 3000 and monitor the parameters of the oxygen sensor, the signal of which should move from 0.1 to 0.9 V.

Reducing the range from 0.2 to 0.7 says that the sensor is faulty. It is worth noting that for 10 seconds, the testimony should be changed from high to low about 9/10 times.

Conclusion

It is important to take into account the fact that Lambda probe is the most vulnerable part of the exhaust system. Official period this mechanism ranges from 40,000 to 80,000 km relative to the age of the car, the state of the motor, fuel and air supply systems, as well as conditions and the rhythm of operation. This means that it is possible to periodically check the voltage, resistance and other operating parameters.

The car's injector system is more economical and efficient than carburetor. This is achieved due to the full control of fuel and air supply, which is carried out by a number of sensors. They perform verification of operating parameters, transmit them to an electronic unit, which analyzes and based on them corrects the operation of the entire system.

And sensors to provide full information The operation of the system is installed not only on the inlet (quantities of fuel, air), but also in exhaust system. It uses only one sensor, but it depends on its operation, how much air will be supplied to the cylinders. It is also called - the oxygen sensor, another name is a lambda probe.

Why do you need a lambda probe in the car?

1) Metal body with thread and hexagon "turnkey";
2) O-ring;
3) the current collector of the electrical signal;
4) ceramic insulator;
5) Wires;
6) wire cuffs sealing;
7) Current contact of the power supply of the heater;
8) external protective screen with a hole for atmospheric air;
9) sensitive element;
10) ceramic tip;
11) Protective screen with opening for exhaust gases.

The main task of this oxygen sensor is an estimate of the number of unburned oxygen in the exhaust gases. The fact is that the most effective combustion of the fuel-air mixture is achieved with a certain ratio of fuel and air - one part of the gasoline should be mixed with 14.7 parts of the air.

If the fuel-air mixture is depleted, the air content is increased, and vice versa - the enriched mixture will provide a smaller percentage of oxygen in exhaust gases. And this is already affected by power, consumption, pickup.

And since the engine works on different modes, Therefore, this ratio is not always observed. To have the ability to control the amount of air supplied, in the power system and the lambda probe is turned on.

Based on the testimony of this sensor, the electronic unit estimates the quality of the fuel and air mixture and when the inconsistency is detected, the system will adjust the operation of the system, providing the optimal mixture by supplying the signal to the nozzles that increase or reduce the amount of fuel injected.

Device and principle of lambda probe

Principle of operation of lambda probe

The principle is like and simple, but the implementation of it is not so easy. This sensor must compare the results with something, to "understand", which occurred a change in the percentage of oxygen. Therefore, it makes measurements in two places - the atmospheric air and the one that remained after the combustion of the mixture. This allows it to "feel" the difference when changing the ratio of the fuel and air mixture.

1 - solid electrolyte ZRO2; 2, 3 - outdoor and internal electrodes; 4 - contact grounding; 5 - "signal contact"; 6 - exhaust pipe

At the same time, an electrical signal should be supplied to the electronic unit. To do this, the lambda probe must be converted to the results of the measurements in the pulse, which will be fed. For measuring the concentration of oxygen in the atmosphere and in exhaust gases, two electrodes that react with it are used. That is, the principle of the galvanic element is involved in this sensor, in which the change of chemical reaction parameters entails a change in the voltage between the sensor electrodes. So, when the mixture is enriched, when the percentage of oxygen is less, the voltage increases, and during the delicate it is reduced.

The electrical pulse resulting as a result of the chemical reaction is fed to the ECU, the parameters of which it compares with the memory prescribed in its memory and as a result, the power system is adjusted.

Using chemical reactions to work, the lambda probe is not difficult in design. Its the main element is a ceramic tip made of zirconium dioxide (less often - titanium dioxide) with a platinum coating, which acts as electrodes that react. One of its side the tip is in contact with the atmosphere, and the other with exhaust gases.

Lambda probe heated

The peculiarity of the work of such a ceramic tip is that the product of effective measurements of the residual percentage of oxygen is performed only at a certain temperature mode. To the tip gained the necessary conductivity, a temperature is required in 300-400 degrees. FROM.

To ensure the necessary temperature regime initially, this sensor was installed closer to the exhaust collector, which ensured the achievement of the required temperature as heated power plant. That is, he did not enter the work immediately. Before the lambda probe begins to transmit pulses, the electronic unit was based on the testimony of other sensors included in the power system, but the optimal mixture formation was not respected.

Video: How to connect a lambda probe heated

Something useful for you:

Some models of lambda probes in their design have special electric heatersWhat provides a faster access to the necessary temperature mode. The heater washing from the on-board network of the car.

The sensor performing its work due to the chemical reaction was the name of the two-point, due to the fact that measurements are made in two places. But another type of lambda probe is also produced - broadband, which is a more modern version of the sensor. In its design, the two-point element is also used, as well as another ceramic element - pumping. At the same time, the essence is reduced to the same supply of an electrical signal to the ECU.

Use two or more sensors

Now many cars to increase their environmental friendliness are used to reduce harmful emissions into the atmosphere. In this case, the exhaust system is not equipped with one, but two and more oxygen sensors.

In such an exhaust system, these sensors produce not only measurement of residual oxygen, but also evaluate the efficiency of the neutralizer. One of the sensors is installed in front of the catalyst, and the second is behind it. This allows on the basis of a comparison of the testimony of two lambda-probes to understand whether neutralization is performed harmful substances.

On the one hand, such a system allows less to pollute the environment, but on the other - it is very "capricious". One or two refills with poor-quality gasoline can easily spoil the neutralizer. And it will already be reflected in the testimony oxygen sensors, and as a result - at the work of the entire power system.

In addition, even when all the operating conditions are met, the neutralizer will fail, since it has its own resource after which it is subject to replacement to restore the normal performance of the power system. And since the replacement is "pleasure" costly, then different tricks come to revenue.

Many simply, and in its place there is a plane sensor - the usual cut of the pipe of the required diameter. And in order to get the difference in the readings of two sensors, use the so-called lambda snapshot probe - a special spacepan installed on the second lambda probe.

This cheating simply removes the tip from the flow of exhaust gases, which affects its testimony. Due to this, the difference is achieved, which the ECU perceives how the operation of the catalyst.

Video: Lambda probe (oxygen sensor). How to fool the second lambda probe

Signs of oxygen sensor malfunction

The lambda probe is a fairly important element in the power system of the car and its breakdown can significantly affect the operation of the power plant. Signs of malfunction as such:

• increase in gasoline consumption;
• "Floating" costs at idle;
• reduction of overclocking dynamics;
• clicks and crash from under cars after stopping the motor;

One of the peculiarities of the lambda probe lies in the fact that its fault is not always recognized by the system of self-diagnosis of the car. In addition, it is impossible to check it with the help of conventional measuring instruments in garage conditions. Its performance is checked only by the oscilloscope.

He is also not maintained. The only thing that can be eliminated is to break the wiring leading to the sensor. But there are also such malfunctions as damage to the heating element and the loss of sensor sensitivity.

Video: How to check lambda probe

Replacement

Therefore, many motorists are not trying to diagnose the performance of lambda probes, but simply periodically produce its replacement for a new one. To maintain the performance of the power system in working condition, it should be replaced once every 2-3 years.

This operation is not difficult and it is performed on observation pit. Pre-acquire the desired sensor model. Before dismantling, the block of wires from the probe is turned off, and then it is unscrewed from its landing location by the horn key of the corresponding size. Processing is allowed to facilitate unscrewing special means (WD-40 or other). The wiring is screwed into the place of the outflow element and the wiring is connected to it.

The name of this sensor comes from the letter of lambda from the Greek alphabet, in the automotive industry it denotes an excess air CF contained in the fuel and air mixture. In fact, such a device is a sensor to determine the composition of exhaust gases.
Excess air is measured by measuring the residual oxygen content in the gases, so the lambda sensor is placed in the graduate manifold in front of the catalyst. The electrical signal of the lambda probe is accepted electronic block Control (or ECU) fuel injection system, which optimizes the composition of the mixture by changing the amount of fuel going to the cylinders.
On some models, another sensor is installed. It is located at the output of the catalyst, which allows to achieve greater accuracy of the composition of the mixture and control the operation of the catalyst.

Principle the Lambda probe It has a design with electroplating elements and a solid ceramic electrolyte made of zirconium dioxide. The ceramics caused yttrium oxide, porous conductive platinum electrodes are deposited from above, of which one "inhales" exhaust, in the second air from the atmosphere.
Lambda probe starts measurement after heating to a temperature in 300-400 ° C. In such conditions, the zirconium electrolyte conducts a signal, and due to the difference of the remaining air and external air remaining in the exhaust leads to the appearance on the output voltage electrodes. A feature of this sensor is a jump-shaped voltage change in the deviations of the mixture of only 0.3%. Thus, the first to which the lambda sensor affects is the voltage on the electrodes.
In addition to zirconium-based sensors, sensors can be interpreted, in the production of titanium dioxide. Such lambda probes operate on the principle of resistance change when the composition of exhaust gases changes. As a result, it turns out that this type sensors are not capable of generating EMF.
Also performed sensors with additional heating. Such a device contributes to a speedy entry to the required range and more accurate data reflection.

Where is the lambda probe?

For understanding where to look for an oxygen sensor, you need to know when a car is produced. In cars issued until 2000, only 10% of cases have been installed 2 sensors. In cars, created after 2000, installed from 2 to 4 lambda probes.
The number of lambd in machines produced after 2000 depends on the volume power aggregate. If the motor volume is less than 2.0 liters, then 2 sensors are installed:

• The first is installed in the podcast space, it is not well noticeable and is easily replaced;
• The second sensor is installed under the bottom of the car.

If the volume of the engine is more than 2.0 liters, then 4 lambda probes are installed:

• 2 sensors (upper, adjusting) - right and left, are also installed in the subcontrol space, they are well noticeable and interchangeable;
• Another 2 sensors (lower diagnostic) - right and left, are installed under the bottom of the car.

Now, to find the first sensors located in the procession space, you must perform the following steps:

Open the hood of the car.

1. Find the engine. It is usually located under a plastic lid in the middle of the boost space.
2. Carefully examine the space around the power unit and find the adjacent massive metal pipes that go deep into the boobspace space. These pipes are an exhaust manifold and serve to remove exhaust gases from the engine. The exhaust manifold can be closed with a heat shield, in this case it will have to be removed.
3. Next, it is necessary to inspect the exhaust collector - it is necessary to find a small cylindrical part in its design (5-7 cm long). One end of this part is screwed into the collector, and a thick wire stretches from the other, which is a lambda probe sensor.
4. In the absence of a sensor on a graduate manifold, trace the pipe that goes deep into the pump-space - Lambda probe is located on it.

There are bellows of two types: mechanical and electronic.

Flands of mechanical type

If it was selected mechanical Type Devices, then the catalyst is usually installed "Space". This item is made of heat-resistant steel either from bronze, and its size is strictly defined. The spacer is done a small hole through which exhaust gases fall.

Gas interact with ceramic crumb placed inside the spacer and pre-coated with a catalytic layer. And as a result of such interaction, oxygen is oxidized with CH and CO, which leads to a decrease in the content of harmful substances.
It is very a budget option Sensor. Mechanical destruction is equally suitable for any car, imported or domestic.

Electronic cheating

Electronic lambda probe It is much more complicated, and we are not talking about "self-defense" ways to create car enthusiasts. They themselves build a snap using one resistor or one condenser. There are enough technological devices (emulators) with a microprocessor.
Such emulators allow to ensure the correct functioning of the control unit (ECU), and not just deceiving it. The microprocessor mounted in the device can estimate the state of the exhaust gases, to analyze the signal processing sent by the first sensor so that after that it will create a signal that will correspond to a signal from a second probe lambda with a good catalyst.

The oxygen sensor is installed on the injection vases (except for the first models with the Bosch 1.5.4 controller).

Oxygen sensor is an integral part of the engine power system. This sensor is designed to estimate the state of the exhaust (the presence of oxygen in the exhaust). In other words, this sensor, focusing on the amount of oxygen in the exhaust, regulates the working mixture.

The oxygen sensor also has a second, but no less popular name "Lambda Probe". Remember that the oxygen sensor and the lambda probe is the same sensor.

Principle of operation of the oxygen sensor (lambda probe)

The working surface of the sensor is a ceramic material covered with platinum.

Operating temperature The sensor is 350 degrees Celsius and above. Therefore, before heating the lambda probe, the first 5 minutes after starting the engine, the working mixture is adjustable by the readings of other sensors of the engine power system. To speed up the heating of the sensor to operating temperatureThe electric heater is mounted.

The principle of the sensor is as follows: the exhaust gases cover the working surface of the lambda, which in turn responds to the difference in the level of oxygen in exhaust gases and the environment. Then it sends a signal that in turn regulates the working mixture.

Where is the oxygen sensor (lambda probe)?

For engine 1,5l

Lambda probe (at number 11) is installed in the exhaust system on the receiving pipe. Screws from the top, in front of the resonator or spacer (if there is no resonator). In other words: put a car on the pit, and look for the sensor sticking to the top throughout the exhaust system. The oxygen sensor is the only sensor that is installed in the exhaust system - therefore do not mishash.

For engine 1.6l

Engine exhaust system 1.6l

Exhaust system this engine Some different is different exhaust system 1.5l. Pay attention to Figure: In this exhaust system, 2 oxygen sensors (number 2) are planned - both are on a roller tollector. These motors are installed as 1 and 2 oxygen concentration sensors: Euro-2 toxicity rate - 1 oxygen sensor, Euro-3 - 2 oxygen sensor.

How often to change the oxygen sensor?

The resource of the VAZ lambda probe is 80-160t. KM, depending on the quality of gasoline and other important moments. The service replacement of the oxygen sensor on the vases of the manual should be held at a mark of 60-70 t.km.

As proper, in the daily operation of the car, the owners turn off the oxygen sensor, flashing brains ().

Can I just turn off the sensor?

Many are asked: Is it possible to turn off the sensor by disconnecting the connector? And what will it lead to?

Answer: Disconnecting the sensor connector, the computer goes to exemplary parameters, so the mixture will be rich - then the poor, the flow will increase, the dynamics will disappear. If you do in the mind, you can turn off the sensor, reflashing the brains using chip-tuning or simply replace the sensor to the new one.

Signs of oxygen sensor malfunction

1. Large gasoline consumption (from 12l or more). By this sensor, big flow Fuel may be for other reasons ()
2. Unstable idling. Also, the reasons for this malfunction can be: dead, etc.
3. Dips when accelerating, dropping the dynamics and engine power. Also, the reasons for low speakers can be fault in the following elements:, low, etc.

Why dies lambda probe?

We have already clarified above that the resource of the oxygen sensor is 80-160 t.km. Probably, you have a question: why such a scatter in a resource, as many as 80 t.km? In fact, the sensor resource depends on the conditions in which the car was operated:

• poor gasoline, in the exhaust of which contains many lead and iron, clog the electrodes of the sensor for several fasteners;
• bad condition mastery rings, caps. Because of them, the oil can fall into the mixture, and with it in the exhaust system;
• due to the clamping valves, cotton is broken into the exhaust system, which destroy the operating surface of the sensor;
• due to improper mixture, the ignition advance angle, as a result of which the sensor overheats, cracks from high temperatures Neutral or catalyst.

How much is the oxygen sensor?

The price of the lambda probe varies from the region and the model from 1000 to 2000.

To modern vehicles Fully strict requirements for the content of harmful substances in the exhaust gases are presented. The required exhaust cleanliness is provided immediately by several car systems, which build their work on the basis of the indications of the set of sensors. Nevertheless, the main responsibility for the "neutralization" of exhaust gases falls on the shoulders of the catalytic neutralizer embedded in the release system. The catalyst is due to the characteristics of the chemical processes inside it is a very sensitive element that flows the flow to the input with a strictly defined component composition. In order to ensure it, it is necessary to achieve the most complete combustion of the engine of the working mixture entering the engine cylinders, which is possible only with the air / fuel ratio, respectively, 14.7: 1. With such a proportion, the mixture is considered ideal, and the indicator λ \u003d 1 (the ratio of the real amount of air to the necessary). Poor working mixture (excess oxygen) corresponds to λ\u003e 1, rich (oarsaturation by fuel) - λ<1.

The accurate dosage is carried out by the controller controlled by the electronic injection system, but the quality of the mixing is still necessary to control somehow, since deviations from the specified proportion are possible in each particular case. This task is solved using the so-called lambda probe, or an oxygen sensor. We will analyze his design and principle of work, as well as let's talk about possible faults.

The device and operation of the oxygen sensor

So, the lambda probe is designed to determine the quality of the fuel-air mixture. This is done by measuring the amount of residual oxygen in exhaust gases. The data are then sent to the electronic control unit, which makes the composition correction of the mixture towards the depletion or enrichment. The place of installation of the oxygen sensor is the exhaust manifold or the fuel reception tube. The car can be equipped with one or two sensors. In the first case, the lambda probe is installed in front of the catalyst, in the second - at the entrance and outlet of the catalyst. The presence of two oxygen sensors makes it possible to more subtly on the composition of the working mixture, as well as control how effectively the catalytic converter performs its function.

There are two types of oxygen sensors - ordinary two-level and broadband. The usual lambda probe has a relatively simple device and generates a waveform signal. Depending on the presence / absence of a built-in heating element, such a sensor may have a connector with one, two, three or four contacts. A constructive conventional oxygen sensor is a galvanic element with a solid electrolyte, the role of which performs ceramic material. As a rule, it is zirconium dioxide. It penetrates for oxygen ions, but the conductivity occurs only when heated to 300-400 ° C. The signal is removed from two electrodes, one of which (internal) is in contact with the stream of exhaust gases, another (external) - with atmospheric air. The potential difference at the conclusions appears only in contact with the inside of the exhaust gas sensor containing residual oxygen. The output voltage is usually 0.1-1.0 V. As already noted, the prerequisite for the operation of the lambda probe is the high temperature of the zirconium electrolyte, which is supported by the built-in heating element, driven from the on-board network of the car.

Injection control system, receiving a lambda-probe signal, tends to prepare the perfect fuel-air mixture (λ \u003d 1), the combustion of which leads to the appearance of a voltage sensor 0.4-0.6 V. If the mixture is poor, then the oxygen content in the exhaust is large, so it occurs Only a small potential difference (0.2-0.3 c). In this case, the duration of the pulse to open the injectors will be increased. Excessive enrichment of the mixture leads to almost complete combustion of oxygen, and it means that its content will be minimal in the release system. The potential difference will be 0.7-0.9 B, which will be a signal to reducing the amount of fuel in the working mixture. Since the engine operation mode is constantly changing, then the adjustment occurs continuously. For this reason, the voltage value at the output of the oxygen sensor fluctuates to the other side relative to the average value. As a result, the signal is wave-like.

The introduction of each new standard, tightening emission standards, improves the requirements for the quality of mixing in the engine. Conventional zirconium-based oxygen sensors are not distinguished by a high level of signal accuracy, so they are gradually displaced by broadband sensors (LSU). Unlike its "fellow", broadband lambda probes measure data in a wide range of λ (for example, modern Bosch probes are capable of reading values \u200b\u200bat λ from 0.7 to infinity). The advantages of the sensors of this type are the ability to control the composition of the mixture of each cylinder separately, the rapid response to the changes occurring and a short time required to turn on to work after starting the engine. As a result, the motor operates in the most economical mode with minimal exhaust toxicity.

The design of the broadband lambda probe assumes the presence of two types of cells: measuring and pumping (pumping). They are separated between themselves diffusion (measuring) gap 10-50 μm wide, in which the same composition of the gas mixture is constantly maintained, corresponding to λ \u003d 1. This composition provides voltage between electrodes at 450 mV. The measuring gap is separated from the flow of exhaust gases by a diffusion barrier used to pump or pump oxygen. With a poor working mixture, exhaust gases contain a lot of oxygen, therefore it is pumped out of the measuring gap using the "positive" current supplied to the pump cells. If the mixture is enriched, then oxygen, on the contrary, pumps into the measurement area, for which the direction of the current changes to the opposite. The electronic control unit reads the value of current consumed by pump cells, finding it equivalent to the lambda. The output signal of the broadband oxygen sensor usually has a curve form slightly deflected from a straight line.

LSU type sensors can be five or six-contact. As in the case of two-level lambda probes, the presence of a heating element is required for their normal functioning. The operating temperature is about 750 ° C. Modern broadbands are warmed in just 5-15 seconds, which guarantees the minimum of harmful emissions during the engine start. It is necessary to ensure that the sensor connectors are not strongly contaminated, since the air enters them inside as a reference gas.

Signs of lambda probe fault

Oxygen sensor is one of the most vulnerable elements of the engine. The service life is limited to 40-80 thousand km of mileage, after which interruptions may be observed. The complexity of the diagnosis of malfunctions associated with the oxygen sensor is that in most cases "dies" is not immediately, but begins to gradually degrade. For example, the response time is increasing or incorrect data is transmitted. If for some reason the ECU completely ceased to receive information about the composition of the exhaust gases, it begins to use the averaged parameters in the work, under which the composition of the fuel-air mixture is far from optimal. Signs of failure of the lambda probe are:

• Increased fuel consumption;
• Unstable operation of a motor at idle;
• Deterioration of the dynamic characteristics of the car;
• Increased CO content in exhaust gases.

The engine with two oxygen sensors is more sensitive to faults that occur in the correction system. When breakdown, one of the probes is almost impossible to ensure the normal functioning of the power unit.

There are a number of reasons that can lead to premature breakdown of lambda probe or reduce its service life. Here is some of them:

• Use of poor quality gasoline (eaten);
• Injection system malfunctions;
• Ignition passage;
• Strong wear of parts of the CPG;
• Mechanical damage to the sensor itself.

Diagnostics and interchangeability of oxygen sensors

Check the health of the simple zirconium sensor in most cases can be using a voltmeter or oscilloscope. The diagnosis of the probe itself consists in measuring the voltage between the signal wire (usually black) and the mass (may be yellow, white or gray). The resulting values \u200b\u200bshould vary for about once in one or two seconds from 0.2-0.3 V to 0.7-0.9 V. It must be remembered that the correct readings will be only with the full warning of the sensor, which will be guaranteed after reaching the engine operating temperature. Malfunctions may concern not only the measuring element of the lambda probe, but also the heating circuit. But usually a violation of the integrity of this chain is recorded by a self-diagnosis system that records the error code into memory. You can also detect the rupture by measuring the resistance on the heater contacts, pre-disconnecting the sensor connector.

If you independently determine the performance of the lambda probe did not work out or there are doubts about the correctness of the measurements made, it is better to contact a specialized service. It is necessary to accurately establish that the problems in the operation of the engine are associated with the oxygen sensor, because its cost is quite high, and the malfunction can be caused by absolutely different reasons. Do not do without the help of specialists and in the case of broadband oxygen sensors, for the diagnosis of which specific equipment is often used.

Faulty lambda probe is better to change the sensor of the same type. The installation of analogs recommended by the manufacturer, suitable by parameters and number of contacts. Instead of sensors without heating, a probe with a heater can be installed (the inverse replacement is not possible), however, in this case it will be necessary to pave additional heating chains.

Repair and replacement of lambda probe

If the oxygen sensor was operated for a long time and failed, then the sensitive element itself stopped performing its functions. In such a situation, the only solution is to replace. Sometimes it begins to collect a new one or worked at a very long lambda probe. The reason for this may be the formation on the housing or the working element of the sensor of various types of sediments interfering with normal functioning. In this case, you can try to clean the probe using orthophosphoric acid. After carrying out the cleaning procedure, the sensor is washed with water, dried and installed on the car. If, using such actions, the functionality cannot be restored, then there is no other path except for buying a new copy.

When replacing the lambda probation, it is necessary to follow certain rules. Unscrew the sensor better on the engine cooled to 40-50 degrees, when thermal deformations are not as large and the parts are not strongly hot. When installing, it is necessary to lubricate the threaded surface with a special sealant eliminating the harness, and also make sure the integrity of the gasket (sealing ring). Tightening is recommended to be carried out with a mounted manner that provides the desired tightness. When connecting the connector, it will not be superfluous to check the wiring harness for damage. After Lambda probe is in its place, tests are carried out at various engine operation modes. Confirmation of the correct operation of the oxygen sensor will be the absence of listed above the signs of malfunction and errors in the memory of the electronic control unit.