What is this service?

Lambda probe - oxygen sensor, installed in the exhaust manifold of the engine. Allows you to estimate the amount of remaining free oxygen in the exhaust gases. The signal from this sensor is used to regulate the amount of fuel supplied. To diagnose a malfunction of this element, it is best to use the "Computer diagnostics of all systems" service. You should not continue to operate a car with a faulty lambda probe, as this can lead to the failure of expensive elements, such as a catalytic converter.

The air-fuel ratio sensor is an integral part of the car engine power system, which allows you to realistically assess the amount of oxygen remaining in the exhaust gases, and thereby adjust the composition of the working mixture by the electronic control unit. When it malfunctions, it is necessary complete lambda sensor replacement.

The main function of the air fuel ratio sensor or lambda probe is to determine the air-fuel ratio in the exhaust gases and estimate the amount of free oxygen in the exhaust gases. Based on its data, the best exhaust gas cleaning, more precise control of the exhaust gas recirculation system and regulation of the amount of fuel injected at full engine load are provided. If it malfunctions, a complete replacement of the sensor is necessary, because it is it that allows you to adjust the composition of the working mixture and ensure the normal operation of the vehicle control system. It is not uncommon for an oxygen sensor to fail. You need to call the wizard, who will check if you need it.

Therefore, at the first signal of the indicator light, stop using the car and tow it to the service, check the condition of the vacuum hoses and the tightness of the exhaust system. It's a simple process that takes about half an hour. This does not require dismantling the engine and removing the protection of the oil pan, it is enough just to dismantle the wheel. So if a specialist comes, let

Keep in mind

A faulty air fuel ratio sensor can cause engine misfiring and mishandling, poor fuel economy and catalytic converter failure.

• maintain your vehicle in good condition and carry out regular maintenance;
• replacement of the lambda probe sensor is necessary at the first light of the indicator light;
• have the vehicle towed to a service center and check the condition of the air fuel ratio sensor.

Let's turn our attention to the output voltage of the B1S1 sensor on the scanner screen. The voltage fluctuates around 3.2-3.4 volts.

The sensor is able to measure the actual air-fuel ratio over a wide range (from lean to rich). The output voltage of the sensor does not indicate rich/lean as a conventional oxygen sensor does. The wideband sensor informs the control unit of the exact fuel/air ratio based on the oxygen content of the exhaust gases.

The sensor test must be carried out in conjunction with the scanner. However, there are a couple more ways to diagnose. The outgoing signal is not a voltage change, but a bidirectional current change (up to 0.020 amps). The control unit converts the analog current change into voltage.

This change in voltage will be displayed on the scanner screen.

On the scanner, the sensor voltage is 3.29 volts with an AF FT B1 S1 mixture ratio of 0.99 (1% rich), which is almost ideal. The block controls the composition of the mixture close to stoichiometric. The voltage drop of the sensor on the scanner screen (from 3.30 to 2.80) indicates the enrichment of the mixture (oxygen deficiency). An increase in voltage (from 3.30 to 3.80) is a sign of a lean mixture (excess of oxygen). This voltage cannot be taken with an oscilloscope, as with a conventional O2 sensor.

The voltage at the sensor contacts is relatively stable, and the voltage at the scanner will change in the event of a significant enrichment or depletion of the mixture, recorded by the composition of the exhaust gases.

On the screen, we see that the mixture is enriched by 19%, the sensor readings on the scanner are 2.63V.

These screenshots clearly show that the block always displays the real state of the mixture. The value of the parameter AF FT B1 S1 is the lambda.

INJECTOR.................2.9ms ENGINE SPD..............694rpm AFS B1 S1................ 3.29V SHORT FT #1............. 2.3% AF FT B1 S1............. 0.99 What type of exhaust? 1% rich	Snapshot #3 INJECTOR.................2.3ms ENGINE SPD............1154rpm AFS B1 S1................ 3.01V LONG FT #1................4.6% AF FT B1 S1............. 0.93 What type of exhaust? 7% rich
Snapshot #2 INJECTOR.................2.8ms ENGINE SPD............1786rpm AFS B1 S1................ 3.94V SHORT FT #1.............. -0.1% LONG FT #1............... -0.1% AF FT-B1 S1............... 1.27 What type of exhaust? 27% lean	Snapshot #4 INJECTOR.... 3.2ms ENGINE SPD..............757rpm AFS B1 S1................ 2.78V SHORT FT #1.............. -0.1% LONG FT #1................4.6% AF FT B1 S1............. 0.86 What type of exhaust? 14% rich

Some OBD II scanners support the option of broadband sensors on the screen, displaying voltage from 0 to 1 volt. That is, the factory voltage of the sensor is divided by 5. The table shows how to determine the mixture ratio from the sensor voltage displayed on the scanner screen

mastertech Toyota 2.5 volts 3.0 volts 3.3 volts 3.5 volts 4.0 volts

p style="text-decoration: none; font-size: 12pt; margin-top: 5px; margin-bottom: 0px;" class="MsoNormal"> OBD II Scan Tools 0.5 volts 0.6 volts 0.66 volts 0.7 volts 0.8 volts

Air:Fuel Ratio 12.5:1 14.0:1 14.7:1 15.5:1 18.5:1

Pay attention to the top graph, which shows the voltage of the wideband sensor. It is almost all the time about 0.64 volts (multiply by 5, we get 3.2 volts). This is for scanners that do not support wideband sensors and are running EASE Toyota software.

The device and principle of operation of a broadband sensor.

The device is very similar to a conventional oxygen sensor. But the oxygen sensor generates voltage, and the broadband generates current, and the voltage is constant (voltage changes only in the current parameters on the scanner).

The control unit sets a constant voltage difference across the sensor electrodes. These are fixed 300 millivolts. The current will be generated to hold these 300 millivolts as a fixed value. Depending on whether the mixture is lean or rich, the direction of the current will change.

These figures show the external characteristics of a broadband sensor. The current values ​​are clearly visible at different compositions of the exhaust gas.

On these oscillograms: the upper one is the current of the sensor heating circuit, and the lower one is the control signal of this circuit from the control unit. Current values ​​greater than 6 amperes.

Testing of broadband sensors.

Four-wire sensors. Heating is not shown in the figure.

The voltage (300 millivolts) between the two signal wires does not change. Let's discuss 2 testing methods. Since the operating temperature of the sensor is 650º, the heating circuit must always be running during testing. Therefore, we disconnect the sensor connector and immediately restore the heating circuit. We connect a multimeter to the signal wires.

Now we will enrich the mixture at XX with propane or by removing the vacuum from the vacuum fuel pressure regulator. On the scale, we should see a change in voltage as when a conventional oxygen sensor is working. 1 volt is the maximum enrichment.

The following figure shows the reaction of the sensor to the lean mixture, by turning off one of the nozzles). The voltage is then reduced from 50 millivolts to 20 millivolts.

The second test method requires a different multimeter connection. We turn on the device in a line of 3.3 volts. We observe the polarity as in the figure (red +, black -).

Positive current values ​​indicate a lean mixture, negative values ​​indicate a rich mixture.

When using a graphical multimeter, this is the current curve (we initiate a change in the composition of the mixture with a throttle valve). Vertical scale current, horizontal time

This graph shows the operation of the engine with the injector turned off, the mixture is lean. At this time, the scanner displays a voltage of 3.5 volts for the sensor under test. A voltage above 3.3 volts indicates a lean mixture.

Horizontal scale in milliseconds.

Here the nozzle is turned on again and the control unit tries to reach the stoichiometric composition of the mixture.

This is how the current curve of the sensor looks like when opening and closing the throttle from a speed of 15 km / h.

And such a picture can be reproduced on the scanner screen to evaluate the operation of a broadband sensor using the parameter of its voltage and the MAF sensor. We pay attention to the synchronism of the peaks of their parameters during operation.

The ideal ratio of gasoline and air , in which the entire mixture burns completely is considered stoichiometric (ideal). The engine works well if the gasoline + air mixture burns well. The mixture burns well if it is optimal. The mixture is optimal if 1 g of gasoline is supplied to 14.7 g of air. The optimal fuel-air mixture burns as quickly as possible and gives the right amount of energy without unnecessary heat. The main thing in the optimal formation of the fuel-air mixture is the DMRV.

AFR is the ratio of air to fuel in an engine's combustion chamber.

Ideal ratio fuel and air for gasoline engines(stoichiometric mixture) = 14.7/1 (AFR) for petrol/diesel.

14.7 g of air per 1 g of gasoline.

Each fuel needs its own fuel/air ratio.

Lean or rich mixture.The air-fuel mixture can be lean or rich.

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Poor mixture (injector), signs and consequences

Mixture setting

While driving Pilot see in real time which mixture is lean or rich.

Poor mixture signs- a stalling engine, more than 14.7 g of air, ignites faster and is accompanied by excessive heating .. Such a mixture is prone to detonation, at low speeds it is not scary. At full load, mixture 14 is already considered hazardous. Doing the whole system on a mixture of 14.7 is not reasonable. At low revs, this will not be enough for acceleration, and at higher revs, you will simply catch detonation.

Poor mixture consequences- at high speeds, with a full load, the level of detonation reaches catastrophic consequences. Piston burnt or fused, valves or spark plugs burnt out. Rising temperatures and loss of power are the simplest things that can happen to an engine when knocking. Usually it is a jammed and overheated motor.

On VAF "e, the consumption was about 25 liters in the city, and on a normally configured converter,15 l in the city, so consider the benefit. I thank smart, honest, temperamental for feedback and dissemination of information.

Rich mixture (injector), signs and effects

Mixture setting

richmix signs

• Fuel consumption has risen sharply.
• Exhaust gases are black or grey.
• Air is less than 14.7g, safer and more reliable for the engine.

A rich mixture of consequences - long-term operation of the engine on a rich mixture can lead to piston failure and failure of the spark plugs.

While driving Pilot records the operation of the oxygen sensor and the air flow sensor. At the same time, it is possible see in real time whether the mixture is lean or rich.

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Reasons for the formation of a rich mixture of an injection engine

• injectors deliver too much fuel
• air filter clogging
• poor throttle performance
• fuel pressure regulator malfunction
• air flow sensor malfunction
• evaporative emission system malfunction
• incorrect operation of the economizer.

It works on cars that do not work on traditional methods such as spacers for lambda probes and circuits such as a capacitor + resistor. Electronic emulator Lambda probe Catalyst 2-channel Pilot .. For engines with two catalysts and two additional oxygen sensors - you need to buy one emulator. Support for lambda probes with offset signal ground. ElectI thank smart, honest, temperamental for feedback and dissemination of information.

lambda sensor

The readings of the lambda sensor are the ratio of the current mixture to the ideal one.

Example: current mixture - air 12.8 g. Lambda sensor readings 0.87=12.8 / 14.7

The ECU takes into account the readings of the lambda sensor only with uniform movement.

When accelerating, braking and warming up, the ECU does not take into account the readings of the lambda sensor and works according to the program.

When tuning, you need to catch the transition from a lean mixture to a rich one. From this point to do a little richer.

In this case, the lambda sensor jumps from 0 to 1. The transition point is approximately 0.45.

For other modes of engine operation, a broadband sensor is used.

The reached maximum speed - about 200-210 km / h did not measure the dynamics, but in the test run they somehow crossed with the E39 M50B20, well, they lit it - it turned out that he is not my rival in terms of dynamics neither from the bottom, nor at three-digit speeds. The actual consumption fluctuates around 11l of the 92nd. Replacing the flow meter with a non-native one without firmware! + mix setting Converter Pilot + BLUETOOTH I thank smart, honest, temperamental for feedback and dissemination of information.

Air is central to optimal education fuel-air mixture is DMRV

Accurate injection of gasoline is easier than precise injection of air. Errors in the calculation of the incoming air lead to problems in the operation of the engine. The errors will be smaller if the air flows in a uniform flow. Flow uniformity is created:

• smooth duct walls
• smooth turns of the air duct (1- 2)
• the absence of pulsations and swirls (remove everything that leads to this from the flow, especially the "nulevik" filter)

If everything is in order along the gasoline supply line, then the main thing in the optimal formation of the mixture is the DMRV (mass air flow sensor). Based on its signals, the ECU supplies gasoline. At the exit there is a "controller" (lambda probe) and "sniffs" the exhaust gases. It determines what is a lot - gasoline or air and informs the ECU. The ECU adjusts the fuel supply.

When you change the flow meter to a non-original one (VAF to MAF), then:

• constructively change the direction for the air flow - this is very important
• should solve the problem with the inlet air temperature sensor (if it is missing, it will not start in winter)
• and most importantly, put a "translator" for the ECU so that the ECU understands which signal of the old flow meter corresponds to the signal of the new flow meter (these are devices such as the Pilot VAF / MAF converter, MAF Emulator 3, "Winners Sensor" (Winners)).
• after all changes, the mixture needs to be adjusted.

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Inlet air temperature sensor

There are two ways to solve the problem of the intake air temperature sensor:

1. put a resistor instead of it and the ECU will think that you have summer +20 all year round
2. open the VAF and remove the sensor from it, and install it in the intake manifold (according to the results, this option is better)

Engine

The engine has several modes of operation:

• idle and warm up
  

neutral, gearbox not connected

idling with the box connected, standing at a traffic light

• uniform motion
• acceleration, braking - smooth
• acceleration (WOT), braking - sharp

Harsh acceleration, braking - this is a sharp effect on the air flow (throttle). We get ripples and swirls.

Sharp acceleration - a lot of air, but little gasoline. Add gasoline in an emergency - the accelerator pump should turn on.

Hard braking - little air, a lot of gasoline. Add air in an emergency - an additional air supply channel should open.

For both modes - the "retarder" of the throttle opening should work. The throttle valve assembly is equipped with a smooth gas release system - a purely mechanical damper system that slows down not abruptly, but smoothly when the accelerator pedal is released. It seems that it was precisely its adjustment that made it possible, at least now it has been verified that this is the case, to ensure a smooth decrease in engine speed without jittering.

Solving the problem with poor engine performance:

• check everything related to the supply of gasoline
• check everything related to the air supply

Action algorithm:

1. Count errors.
2. If item 1 is not fulfilled, then we logically determine which is more gasoline or air. Or the smell from the exhaust pipe. The color of the candles.
3. Determined - gasoline is low.
4. We go along the line of supply of gasoline:

• Mechanics(part wear, deformation, accelerator pump, gas pump, fuel filter, injectors, fuel pump mesh, gas tap, small passage hole inside the tap. Corrected: by replacing the tap or drilling.),
• electrician(contacts, wires, correct connection),
• time trigger(injector keys, ignition angle, distributor, candles),
• temperature triggered-worse for hot (some part heated up and the gap between it and the neighboring one decreased, friction appeared or the gap increased and there was no contact - the timing belt, the tension roller just dangled, the camshafts were out of sync with the crankshaft and the engine stalled. , bypass roller, spring, DTVV, DTOZH)

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Setting the air/fuel mixture (AFR)

The purpose of tuning is to get maximum power and maximum torque during hard acceleration, with moderate consumption in city and on the highway.

There are two ways to set up a mixture:

1. trimming resistor - a limited range ("Sensor Winners" (Winners)). Before that, be sure to set the basic settings through VAGCOM.
2. using software (MAF Emulator 3, Pilot VAF/MAF). The software from MAF Emulator 3 is configured for broadband lambda, and the software from the Pilot VAF / MAF converter is configured for conventional lambda.

Set up step by step:

1. XX setting,
2. further adjustment of overclocking.
3. The most correct is the uphill mode.
4. If you can tune the engine as efficiently as possible in this mode, then consider that the tuning was a success. Never set the entire rpm range in neutral.

The higher the speed, the richer the air-fuel mixture, and the earlier the ignition angle.

Don't forget before you start set the mechanical ignition timing according to the stroboscope.

Electronic emulator+ BLUETOOTH Lambda Probe Catalyst 2 Channel Pilot 1. There is a setting for emulation parameters
2. There is logging - recording of all emulation parameters while the car is moving
3. Engine type: any 4. Installation: open circuit
5. Programming: Yes
6. Diagnostics saved
7. Before being sent to the client, it undergoes a mandatory parameter setting and performance test.
8. Support Euro 3, 4, 5, 6
9. No intervention in the software part of the computer
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Increased emissions of harmful substances occur when the air-fuel ratio in the mixture is not adjusted correctly.

Fuel-air mixture and engine operation

The ideal ratio of fuel and air for gasoline engines is 14.7 kg of air per 1 kg of fuel. This ratio is also called the stoichiometric mixture. Virtually all gasoline engines are now powered by the combustion of such an ideal mixture. The oxygen sensor plays a decisive role in this.

Only at this ratio, complete combustion of the fuel is guaranteed, and the catalyst almost completely converts harmful exhaust gases hydrocarbon (HC), carbon monoxide (CO) and nitrogen oxides (NOx) into environmentally friendly gases.
The ratio of the actual air used to the theoretical demand is called the oxygen number and is denoted by the Greek letter lambda. For a stoichiometric mixture, lamba is equal to one.

How is this done in practice?

The composition of the mixture is controlled by the engine control system ("ECU" = "Engine Control Unit"). The ECU controls the fuel system, which supplies a precisely metered fuel-air mixture during the combustion process. However, for this, the engine management system needs to have information whether the engine is currently running on an enriched (lack of air, lambda less than one) or lean (excess air, lambda greater than one) mixture.
This crucial information is provided by the lambda probe:

Depending on the level of residual oxygen in the exhaust gas, it gives different signals. The engine management system analyzes these signals and regulates the supply of the fuel-air mixture.

Oxygen sensor technology is constantly evolving. Today, lambda control guarantees low emissions, efficient fuel consumption and long catalyst life. To achieve the operating state of the lambda probe as quickly as possible, a highly efficient ceramic heater is used today.

The ceramic elements themselves are getting better every year. This guarantees even more accurate
measurement and ensures compliance with more stringent emission standards. New types of oxygen sensors have been developed for special applications, such as lambda probes, the electrical resistance of which changes with the composition of the mixture (titanium sensors), or broadband oxygen sensors.

The principle of operation of the oxygen sensor (lambda probe)

In order for the catalyst to work optimally, the ratio of fuel and air must be very precisely matched.

This is the task of the lambda probe, which continuously measures the residual oxygen content in the exhaust gases. By means of an output signal, it regulates the engine management system, which thereby precisely sets the fuel-air mixture.

Quite stringent requirements for the content of harmful substances in exhaust gases are imposed on modern vehicles. The necessary cleanliness of the exhaust is provided by several vehicle systems at once, building their work based on the readings of many sensors. But still, the main responsibility for the "neutralization" of exhaust gases falls on the shoulders of a catalytic converter built into the exhaust system. The catalyst, due to the nature of the chemical processes occurring inside it, is a very sensitive element, which must be supplied with a stream with a strictly defined composition of components. To ensure it, it is necessary to achieve the most complete combustion of the working mixture entering the engine cylinders, which is possible only with an air / fuel ratio of 14.7: 1, respectively. With such a proportion, the mixture is considered ideal, and the indicator λ = 1 (the ratio of the actual amount of air to the required one). A lean working mixture (excess oxygen) corresponds to λ>1, a rich one (oversaturation with fuel) - λ<1.

The exact dosage is carried out by an electronic injection system controlled by the controller, however, the quality of mixture formation still needs to be controlled in some way, since deviations from the specified proportion are possible in each specific case. This problem is solved using the so-called lambda probe, or oxygen sensor. We will analyze its design and principle of operation, and also talk about possible malfunctions.

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 the exhaust gases. Then the data is sent to the electronic control unit, which corrects the composition of the mixture towards lean or enrich. The location of the oxygen sensor is the exhaust manifold or the downpipe of the muffler. 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 inlet and outlet of the catalyst. The presence of two oxygen sensors allows you to more subtly influence the composition of the working mixture, as well as control how efficiently the catalytic converter performs its function.

There are two types of oxygen sensors - conventional two-level and broadband. A conventional 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 can have a connector with one, two, three or four pins. Structurally, a conventional oxygen sensor is a galvanic cell with a solid electrolyte, the role of which is performed by a ceramic material. As a rule, it is zirconium dioxide. It is permeable to oxygen ions, however, conductivity occurs only when heated to 300-400 °C. The signal is taken from two electrodes, one of which (internal) is in contact with the exhaust gas flow, the other (external) is in contact with atmospheric air. The potential difference at the terminals appears only when in contact with the inside of the sensor exhaust gases containing residual oxygen. The output voltage is usually 0.1-1.0 V. As already noted, a prerequisite for the operation of the lambda probe is the high temperature of the zirconium electrolyte, which is maintained by a built-in heating element powered from the vehicle's on-board network.

The injection control system, receiving the lambda probe signal, seeks to prepare an ideal fuel-air mixture (λ = 1), the combustion of which leads to the appearance of a voltage of 0.4-0.6 V on the sensor contacts. If the mixture is poor, then the oxygen content in the exhaust is high, therefore only a small potential difference (0.2-0.3 V). 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, which means that its content in the exhaust system will be minimal. The potential difference will be 0.7-0.9 V, which will signal a decrease in the amount of fuel in the working mixture. Since the operating mode of the engine is constantly changing while driving, the adjustment also takes place continuously. For this reason, the voltage value at the output of the oxygen sensor fluctuates in both directions relative to the average value. The result is a waveform signal.

The introduction of each new standard, which tightens emission standards, increases the requirements for the quality of mixture formation in the engine. Conventional oxygen sensors based on zirconium do not have a high level of signal accuracy, so they are gradually being replaced by wideband sensors (LSU). Unlike their "brothers", broadband lambda probes measure data in a wide range of λ (for example, modern Bosch probes are able to read values ​​at λ from 0.7 to infinity). The advantages of sensors of this type are the ability to control the composition of the mixture of each cylinder separately, a quick response to ongoing changes and a short time required to be put into operation after starting the engine. As a result, the engine operates in the most economical mode with minimal exhaust toxicity.

The design of a broadband lambda probe assumes the presence of two types of cells: measuring and pumping (pumping). They are separated from each other by a diffusion (measuring) gap 10-50 μm wide, in which the same composition of the gas mixture is constantly maintained, corresponding to λ=1. This composition provides a voltage between the electrodes at the level of 450 mV. The measuring gap is separated from the exhaust gas flow by a diffusion barrier used to pump or pump oxygen. With a lean working mixture, the exhaust gases contain a lot of oxygen, so 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, is pumped into the measurement area, for which the current direction is reversed. The electronic control unit reads the value of the current consumed by the pumping cells, finding its equivalent in lambda. The output signal of a broadband oxygen sensor typically has a curve that deviates slightly from a straight line.

LSU type sensors can be five- or six-pin. As in the case of two-level lambda probes, a heating element is required for their normal operation. The operating temperature is about 750 °C. Modern broadbands warm up in just 5-15 seconds, which guarantees a minimum of harmful emissions during engine start-up. Care must be taken that the sensor connectors are not heavily soiled, as air enters through them as a reference gas.

Symptoms of a lambda probe malfunction

The oxygen sensor is one of the most vulnerable elements of the engine. Its service life is limited to 40-80 thousand kilometers, after which there may be interruptions in operation. The difficulty in diagnosing malfunctions associated with an oxygen sensor lies in the fact that in most cases it does not “die” immediately, but begins to gradually degrade. For example, the response time increases or incorrect data is transmitted. If, for some reason, the ECU completely stopped receiving information about the composition of the exhaust gases, it begins to use averaged parameters in operation, at 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 the engine at idle;
Deterioration of the dynamic characteristics of the car;
Increased CO content in exhaust gases.
An engine with two oxygen sensors is more sensitive to malfunctions in the mixture correction system. If one of the probes breaks down, it is almost impossible to ensure the normal functioning of the power unit.

There are a number of reasons that can lead to premature failure of the lambda probe or a reduction in its service life. Here are some of them:

The use of poor quality gasoline (leaded);
Malfunctions of the injection system;
misfiring;
Strong wear of CPG parts;
Mechanical damage to the sensor itself.

Diagnostics and interchangeability of oxygen sensors

In most cases, you can check the health of a simple zirconium sensor using a voltmeter or oscilloscope. Diagnostics of the probe itself consists in measuring the voltage between the signal wire (usually black) and ground (may be yellow, white or gray). The resulting values ​​​​should change approximately once every one or two seconds from 0.2-0.3 V to 0.7-0.9 V. It must be remembered that the readings will be correct only when the sensor is fully warmed up, which is guaranteed to occur after the engine reaches operating temperature. Malfunctions can concern not only the measuring element of the lambda probe, but also the heating circuit. But usually a violation of the integrity of this circuit is fixed by a self-diagnosis system that writes an error code to memory. You can also detect a gap by measuring the resistance at the heater contacts, after disconnecting the sensor connector.

If it was not possible to independently establish the operability of the lambda probe or there are doubts about the correctness of the measurements made, then it is better to contact a specialized service. It is necessary to establish precisely that the problems in the operation of the engine are connected precisely with the oxygen sensor, because its cost is quite high, and the malfunction can be caused by completely different reasons. You can not do without the help of specialists in the case of broadband oxygen sensors, for the diagnosis of which specific equipment is often used.

It is better to change a faulty lambda probe to a sensor of the same type. It is also possible to install analogues recommended by the manufacturer, suitable in terms of parameters and number of contacts. Instead of sensors without heating, you can install a probe with a heater (reverse replacement is not possible), however, in this case, it will be necessary to lay additional wires for the heating circuit.

Repair and replacement of lambda probe

If the oxygen sensor was used for a long time and failed, then, most likely, the sensitive element itself ceased to perform its functions. In such a situation, the only solution is to replace. Sometimes a new or a lambda probe that has worked for a very short time starts to fail. The reason for this may be the formation on the body or the working element of the sensor of various kinds of deposits that interfere with normal functioning. In this case, you can try cleaning the probe with phosphoric acid. After the cleaning procedure, the sensor is washed with water, dried and installed on the car. If with the help of such actions the functionality cannot be restored, then there is no other way than buying a new copy.

When replacing a lambda probe, certain rules should be followed. It is better to unscrew the sensor on an engine that has cooled down to 40-50 degrees, when thermal deformations are not so large and the parts are not very hot. During installation, it is necessary to lubricate the threaded surface with a special sealant that prevents sticking, and also make sure that the gasket (o-ring) is intact. Tightening is recommended to be carried out with the torque specified by the manufacturer, providing the desired tightness. When connecting the connector, it is not superfluous to check the wiring harness for damage. After the lambda probe is in place, tests are carried out in various engine operating modes. The correct operation of the oxygen sensor will be confirmed by the absence of the above symptoms and errors in the memory of the electronic control unit.