Oxygen sensor: signs of malfunction. What is a lambda probe (oxygen sensor)? Lambda probe: causes of malfunction Lambda probe either works or not

In internal combustion engines, oxygen determines the optimal ratio of the components of the combustible mixture, the efficiency and environmental friendliness of the engine. A lambda (λ) probe is a device for changing the volume of oxygen or its mixture with unburned fuel in the manifold of a power unit. An understanding of the device and the principle of operation of the sensor will help the owner of the car to monitor its performance, preventing unstable engine operation and excessive fuel consumption.

Purpose and principle of operation of the lambda probe

Lambda probe mounted on the exhaust pipe

Tough environmental requirements for cars are forcing manufacturers to use catalytic converters that reduce the toxicity of exhaust emissions. But its effective work cannot be achieved without monitoring the composition of the air-fuel mixture. Such control is carried out by an oxygen sensor, it is also a λ-probe, the operation of which is based on the use of feedback from the device and a fuel system with a discrete or electronic injection system.

The amount of excess air is measured by determining the residual oxygen in the exhaust gas. For this, the lambda probe is placed in front of the exhaust manifold catalyst. The signal from the sensor is processed by the control unit and optimizes the air-fuel mixture, more precisely metering the supply of fuel from the injectors. On some car models, a second device is installed after the catalyst, which makes the mixture preparation even more accurate.

The lambda probe works as a galvanic cell with a solid electrode made in the form of zirconium dioxide ceramics doped with yttrium oxide, on which platinum sputtering is applied to act as electrodes. One of them records the readings of atmospheric air, and the second - of the exhaust gas. Effective operation of the device is possible when the temperature reaches more than 300 ° C, when the zirconium electrolyte acquires conductivity. The output voltage appears from the difference in the amount of oxygen in the atmosphere and in the exhaust gas.

Oxygen sensor device (lambda probe)

There are two types of λ-probe - broadband and point-to-point. The first type has a higher information content, which allows you to more accurately tune the engine operation. The device is made of materials that can withstand elevated temperatures. The principle of operation of all types of sensors is the same, and consists in the following:

1. The two-point device measures the oxygen level in the engine exhaust and in the atmosphere using electrodes, on which the potential difference changes depending on the oxygen level. The signal is removed by the engine control unit, after which the fuel supply to the cylinders by the injectors is automatically adjusted.
2. Broadband consists of an injection and a point-to-point element. Its electrodes are maintained at a constant voltage of 450 mV by adjusting the pumping current. A decrease in the oxygen content in the exhaust leads to an increase in the voltage at the electrodes. The control unit, after receiving the signal, creates the necessary current on the pumping element for pumping or pumping out air in order to bring the standard voltage. So, with an excessively enriched fuel-air mixture, the control unit sends a command to pump in an additional portion of air, and with a lean mixture it acts on the injection system.

Possible causes of a malfunction of the lambda probe

Appearance of a faulty lambda probe

Like any other device, the lambda probe can fail, but in most cases the car remains on the move, while the dynamics of its movement deteriorates significantly, and fuel consumption increases, which is why the vehicle needs urgent repair. A λ-probe breaks down for the following reasons:

1. Mechanical failure in case of damage or defect of the case, violation of the sensor winding, etc.
2. Poor fuel quality, in which iron and lead clog the active electrodes of the device.
3. Oil entering the exhaust pipe with poor condition of the oil scraper rings.
4. Contact with solvents, detergents or any other operating fluids.
5. "Pops" from the engine due to faults in the ignition system, destroying the fragile ceramic parts of the device.
6. Overheating due to incorrect ignition timing or rich fuel mixture.
7. Application of a sealant when installing the device, containing silicone, or vulcanizing at room temperature.
8. Multiple unsuccessful attempts to start the engine within a short time, which leads to the accumulation of fuel in the exhaust manifold and its ignition, causing a shock wave.
9. A short to ground, poor contact or lack of contact in the input circuit of the device.

Symptoms of a malfunction of the lambda probe

The main malfunctions of a λ-probe are manifested in the following symptoms:

1. Increased overall exhaust gas toxicity.
2. The engine runs unstable at low revs.
3. Excessive consumption of fuel is observed.
4. When driving, the dynamics of vehicle movement deteriorates.
5. When the car stops after driving, a characteristic crackling sound is heard from the catalyst in the exhaust manifold.
6. In the area of ​​the catalytic converter, the temperature rises or it warms up to a red-hot state.
7. The signal of the "SNESK ENGINE" lamp during the steady state of movement.

Methods for checking a lambda probe

Checking the lambda probe with a multimeter

To check the λ-probe yourself, you need a digital voltmeter and a vehicle manual. The sequence of actions is as follows:

1. The wires are disconnected from the probe block and a voltmeter is connected.
2. The car engine is started, the speed is set to 2500 rpm, and then reduced to 2000 rpm.
3. Remove the vacuum tube from the fuel pressure regulator and record the voltmeter reading.
4. At 0.9 V, the sensor is OK. If the voltmeter does not respond at all, or the reading is below 0.8 V, the λ probe is faulty.
5. To check in dynamics, the probe is connected to the connector, connecting a voltmeter in parallel and maintaining the rotation of the engine crankshaft at 1500 rpm.
6. If the sensor is working properly, the voltmeter will show 0.5 V. A deviation from this value indicates a breakdown.

Repair of a lambda probe

If the λ-probe breaks down, it can simply be turned off, and the control unit will switch to average fuel injection parameters. This action will immediately make itself felt in the form of increased fuel consumption and the appearance of an error in the engine ECU. If the lambda probe breaks down, it must be replaced. But there are technologies for "revitalizing" a faulty sensor, which make it possible, with a certain degree of probability, to return it to a working state:

Repair of a lambda probe by soaking in phosphoric acid

1. Washing the device with phosphoric acid at room temperature for 10 minutes. The acid eats away carbon deposits and lead deposited on the rod. In this case, it is important not to overdo it, so as not to damage the platinum electrodes. The device is opened by cutting off the cap at the very base on a lathe, and the rod is dipped in acid, then washed in water and the cap is welded to its original place with argon welding. After the procedure, the signal is restored after 1-1.5 hours of engine operation.

Old and new lambda probe

2. "Soft cleaning" of electrodes with an ultrasonic disperser in an emulsion solution. During the procedure, the appearance of electrolysis of viscous metals deposited on the surface is possible. Before cleaning, take into account the design of the probe and the material of its manufacture (ceramics or cermets), on which inert materials (zirconium, platinum, barium, etc.) are applied. After reconditioning, the sensor is instrumented and returned to the vehicle. The procedure can be repeated many times.

Modern cars are equipped with electronic fuel injection systems with the ability to adjust the composition of the mixture. In the event of a device breakdown, knowledge of the symptoms of a malfunctioning lambda probe will help determine the cause of the problem.

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Description of the device and where it is located

With the advent of electronic gasoline injection systems, the designers were faced with the task of adjusting the composition of the fuel mixture. For this they began to apply. The devices maintain the composition of the fuel mixture within certain limits, which makes it possible to ensure the maximum efficiency of the catalytic converter. With other compositions of the mixture, the neutralizer starts to work incorrectly and fails.

One or two sensors are used depending on the design of the exhaust system:

1. The first is installed directly in the exhaust manifold and measures the composition of the exhaust gases in front of the catalytic converter. On early systems, this device was the only one.
2. With the introduction of Euro-3 standards, a second probe, located after the neutralizer, began to be used. analyzes data from two probes and indirectly evaluates the efficiency of the catalyst, and also corrects the mixture composition.

Lambda probe variants

Manufacturers have set the service life for products:

• a probe without a heating coil - no more than 80 thousand km;
• heated unit - up to 100 thousand km;
• planar (broadband) probes - up to 160 thousand km.

The declared life of the probes is not accurate. The life of the devices depends on many factors and may be less or more than the specified values.

Device diagram

Consider a schematic diagram of the probe that gives an idea of ​​the placement of the nodes. Knowledge of the design allows you to understand the location of the parts that are prone to breakage.

Example of a probe design

The design includes:

• 1 - metal nipple designed for installing the probe, there are turnkey edges on the outer surface, the thread is located below;
• 2 - ceramic insulator;
• 3 - a sealing element for entering a wiring harness;
• 4 - signal wires;
• 5 - metal protective cap, equipped with ventilation ducts, designed to protect the measuring element from damage;
• 6 - spring contact part;
• 7 - a sensitive element made of ceramics;
• 8 - heating rod;
• 9 - ventilation duct;
• 10 - outer metal case.

The main signs and causes of a malfunction of the lambda probe

The main symptoms of a lambda probe malfunction:

• interruptions in operation and floating speed at idle or low shaft speed;
• decrease in the acceleration parameters of the car;
• a noticeable (sometimes by several liters) increase in fuel consumption;
• turning on the Check Engine indicator and the appearance of errors in the memory of the control unit.

The reasons for the malfunction of the oxygen sensor can be:

• damaged sensitive element;
• clogging of the working area of ​​the probe with soot or lead;
• destruction of wiring;
• failure of the heating element.

How to check an oxygen sensor?

If the above problems occur, you need to check the condition of the oxygen sensor. The lambda probe is checked visually and using electronic equipment.

Visual inspection

The very first stage of verification is an external examination of the part, which consists of the following stages:

1. Carry out a visual inspection of the wiring and plugs. Insulation melting, mechanical damage, contact oxidation are inadmissible.
2. The working surface of the sensor should be free of soot and soot deposits. A layer of soot occurs when the piston rings are worn or if the valves are not tight. The soot changes the sensitivity of the probe, which sends incorrect information to the engine control unit. After cleaning the part, the operability is restored. Cleaning is done with a soft brush and keeping the probe in phosphoric acid for 15-20 minutes.
3. If there are white or light gray deposits on the surface of the sensing element, this indicates the use of fuel with additives based on tetraethyl lead. As a rule, such a sensor quickly fails.

An external inspection of the lambda probe allows you to determine only a small part of the malfunctions, a more thorough analysis is performed using a tester or multimeter.

Checking with a multimeter

Heating circuits in the device may burn out or the destruction of the working element may begin. These faults can be detected using electronic test devices.

There are three types of lambda probe plugs:

• two-wire (ground and signal);
• three-wire (the positive power wire of the heating element is added);
• four-wire (there is an additional grounding of the heating coil).

To check the lambda probe, factory documentation is required to determine the purpose of the wires and a digital multimeter switched to voltmeter and ohmmeter modes.

Approximate sequence of actions:

1. Warm up the engine to operating temperature, since only in this case it is possible to read the correct data.
2. Ring heating circuits. Under normal conditions, the resistance is in the range of 2-15 ohms, more accurate data can be obtained from the reference literature. Resistance is measured by connecting to two pins in the plug (for a four-wire probe) or to a pin on the heater and the car body (in a three-wire probe). If the resistance is zero, it means that a short circuit has been detected in the windings of the heating element. The tendency of resistance to infinity is a symptom of breaking nichrome heating threads.
3. Call the wiring to the heater from the control unit for breaks.
4. Check the voltage on the signal circuit. The negative signal can be taken from the car body or directly from the battery terminal. Before checking, the engine should be run at medium speed (2500-3000 rpm) for 2-3 minutes. Disconnect the plug and connect the test device.
5. Bring the revs up to 2500-2600 rpm and abruptly drop the gas pedal. The voltmeter readings are in the range of 0.2-1.0 volts and change at a frequency of 1 Hz (on average, once a second).
6. Disconnect the vacuum tube from the pressure regulator to check the leanness of the mixture. It is possible to forcibly deplete the mixture by closing the air intake hole of the throttle assembly by hand. Measure the voltage, which should be within 0.2 volts or less.
7. Install the tube back.
8. Raise the revs sharply to maximum. In this case, the voltage should be about 1 volt.

An indirect sign of the inoperability of the probe is a stable voltage of about 0.45-0.5 volts, which does not change with the operating mode and the composition of the mixture. However, it is recommended that a thorough check with an oscilloscope or test computer be performed to confirm a breakdown.

Oscilloscope check

The advantage of checking the probe with an oscilloscope is the ability to monitor not only the voltage value, but also the amplitude of the change over time. Shifts in amplitude characteristics within small limits cause changes in engine operating parameters, but are not recorded by the control unit as an error. An oscilloscope check is carried out under the conditions of a specialized service, since the device is rarely found in personal possession.

Sequencing:

1. Warm up the engine.
2. Connect the oscilloscope leads to the sensor.
3. Test at idle speed. Below are some sample oscilloscope waveforms. By the signal amplitude, you can make a conclusion about the state of the part.
4. Replace damaged part and retest.

Examples of oscilloscope graphs

How to check a sensor using ELM327 USB OBD II scanner

The owner can independently test the sensor using the ELM327 scanner that works under the OBD II protocol. The device is compatible with most Russian and foreign cars.

Test sequence:

1. Connect the tester to the diagnostic socket. The location of the connector must be specified in the documentation supplied with the vehicle.
2. Read the operating parameters and transfer them to a laptop with preinstalled special software. The most common utility is Torque Pro, which is open source.

Below is a video tutorial on how the ELM327 scanner works with the Torque Pro utility, provided by the Savontiy channel.

Instructions for replacing the sensor with your own hands

Before starting work, you need to prepare materials and tools:

1. New probe.
2. A wrench or bit that will allow the sensor body to be unscrewed from the manifold. On some vehicles, you can try to remove the device with a 22 mm open-end wrench or gas adjustable wrench. But most of the machines require the use of a specialized attachment.
3. Extension for the nozzle.
4. Torque wrench up to 50-100 N / m.
5. Protective gloves and sleeves, as work is done on a heated manifold.
6. Wrenches for removing the heat shield and / or manifold.

Lambda probes should be changed to the same model or similar, suitable in terms of parameters. It is impossible to install the first available sensor. Before installation, you must carefully study the instructions supplied by the manufacturer.

Approximate sequence of actions when replacing the first probe:

1. Warm up the power unit to operating temperature. In this case, thermal expansion of the elements of the exhaust system occurs, which makes it easier to unscrew the sensor from the manifold or exhaust pipe.
2. Switch off the engine.
3. Remove the terminal from the battery to eliminate the possibility of starting the electric cooling fan.
4. Carefully disconnect the probe connector from the wiring.
5. Wear protective gloves and remove the probe wire from the clips.
6. Unscrew the probe using the nozzle. Difficulties are possible at this stage, since the junction of the probe and the manifold is clogged with rust and burnt grease. To facilitate the process, local heating with a gas burner can be used, which allows you to burn off the rust. After that, you should try to pull the probe from its place, if the part does not start to unscrew, repeat the heating again.
7. Wipe the installation site from the remnants of the old graphite grease.
8. Check for the presence of regular grease on the threads of the new probe. The tool may be included in the delivery set in a separate sachet. The lubricant is applied in a thin, uniform layer to the threads. It is strictly forbidden to apply to the protective cap, as this leads to the formation of solid carbon deposits and deterioration of the probe's performance. If the vehicle is equipped with a two-bolt sensor, they do not need lubrication.
9. Gently screw the sensor into place by hand until it stops.
10. Tighten the probe with a wrench to the required torque. Most manufacturers indicate the force of 40-45 N / m, but it is recommended to clarify the value according to the service literature. In the absence of a torque wrench, tightening is carried out by turning the probe by 180º after tightening it by hand until it stops.
11. Lay the harness along the clips, secure with clamps if necessary.
12. Connect the battery and remove errors from the control unit. Errors are removed using a computer or in another way (depending on the make and model of the car).

When installing the probe, the tightening torque must be observed. Excessive force leads to destruction of the probe body or thread stripping, low torque causes exhaust gas breakthrough and uneven heating of the part.

How to repair a lambda probe?

Manufacturers of lambda probes position the parts as non-separable and irreparable. However, some car owners, with some success, try to disassemble and repair sensors, assembling one working device from two or more damaged devices.

The car owner should remember that such a repair of the lambda probe is a temporary measure. It is recommended to purchase a new sensor and use the repaired one as a spare.

Heating element repair

An approximate sequence for disassembling and repairing a sensor with a damaged heating element:

1. Carefully saw through the outer casing of the sensor.
2. The second sensor is cut in the same way.
3. Remove the heating rods from the sawn bodies. The whole device must be wiped off carbon deposits and dirt with a dry cloth. The use of cleaning agents is not recommended as chemical reactions may damage the heater.
4. Install the heater in the probe to be used on the vehicle.
5. Solder the body with copper-phosphorus solder having a melting point of about 700 ºС. A gas jewelry burner is used as a heat source.
6. Check the performance of the product with a tester and install the probe into the manifold. If the repaired device does not work, then you can try changing the heater again. Below are photographs explaining the repair process.

Repair of faulty wiring

There are recommendations for installing an additional resistor in the heating circuit when it fails. According to the authors' idea, the resulting resistance should give the correct signal to the control unit and turn off information about the error. In fact, this is the case, but the lifespan of additional resistance ranges from several hours to several days. A resistor that heats up to high temperatures can cause a fire in the engine compartment.

You can troubleshoot a broken wire harness as follows:

1. Saw through the body at the top of the probe.
2. Dismantle completely old wires, since the insulation wears out and cracks over time.
3. Remove the pins with soldered wires from the donor block. Any available plug-in block can be used as a donor.
4. For further work, it is necessary to solder the connecting elements from the pins.
5. Assemble a new wire harness using the original rubber seal from the probe.
6. Install the removed connecting elements on the ends of the wires.
7. Connect the wiring with the return cables of the lambda probe.
8. Crimp the contacts and additionally solder with refractory copper-phosphorus solder.
9. Solder the case and coat the place where the wiring harness enters the sensor with a heat-resistant sealant.

Cleaning from carbon deposits and soot

Another repair option is cleaning the measuring element from carbon deposits and soot:

1. Cut off protective caps carefully.
2. Soak the sensor in phosphoric acid, then gently brush off the carbon deposits with a brush. Force is not recommended as the measuring element is extremely fragile.
3. If necessary, clean the element additionally by heating on a gas burner. The procedure should be carried out carefully, as the part may crack. Heating and cooling with cold water recommended in a number of sources is prohibited, since this will lead to complete failure of the probe.
4. Assemble the sensor back by connecting the parts with refractory solder or spot welding.

How much does an oxygen sensor cost?

The cost of the sensor depends on the type of product and the prevalence of the model. Below are the reference prices for the devices used on some car models.

Video "Checking the lambda probe"

Unfortunately, not all car owners know what a lambda probe is and what it is needed for. A lambda probe is an oxygen sensor that allows the electronic system to monitor and balance the correct ratio of air to gasoline in the combustion chambers. It is able to timely correct the structure of the fuel mixture and prevent the destabilization of the engine's working 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 the stable operation of the vehicle.

The principle of operation of the 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 exceeding of this standard value can lead to unpleasant consequences.

With the standard assembly of the car, the lambda probe is mounted in the exhaust manifold in the area of ​​the connection of the pipes, however, sometimes there are other variations of its installation. In principle, a different arrangement does not affect the performance of this instrument.

Today you can find several variations of the lambda probe: with a two-channel arrangement and a broadband type. The first type is most often found on old cars produced in the 80s, as well as on new economy class models. The wideband type sensor is inherent in modern cars of the middle and upper class. Such a sensor is able not only to accurately determine the deviation from the norm of a certain element, but also to balance the correct ratio in a timely manner.

Thanks to the diligent work of such sensors, the service life of the vehicle is significantly increased, fuel consumption is reduced and the stability of maintaining idle speed is increased.

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

The main symptoms of a lambda probe malfunction

The main symptom of a malfunction of the lambda probe is a change in the operation of the engine, since after its breakdown, the quality of the supplied fuel mixture into the combustion chamber significantly deteriorates. The fuel mixture, in fact, remains uncontrolled, which is unacceptable.

The reason for the exit from the operating state of the lambda probe may be the following:

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

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

The gradual failure of the lambda probe can be broken down into several stages. At the initial stage, the sensor ceases to function normally, that is, at certain operating moments of the motor, the device stops generating a signal, after which the idle speed is destabilized.

In other words, they begin to fluctuate in a rather wider range, which ultimately leads to a loss in the quality of the fuel mixture. At the same time, the car begins to twitch for no reason, you can also hear uncharacteristic claps of the engine and the warning light on the instrument panel must light up. All these abnormal phenomena signal the car owner about the incorrect operation of the lambda probe.

At the second stage, the sensor stops working at all on an unheated engine, while the car will signal the problem to the driver in all possible ways. In particular, there will be a noticeable drop in power, slower response when the accelerator pedal is applied and all the same pops from under the hood, as well as unjustified jerking of the car. However, the most significant and extremely dangerous signal of a lambda probe breakdown is engine overheating.

If all previous signals are completely ignored, indicating a deterioration in the state 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 significantly increase and an unpleasant pungent odor with a pronounced shade of toxicity from the exhaust pipe will appear. In modern automated vehicles, in the event of a breakdown of the oxygen sensor, emergency blocking can simply be activated, as a result of which the subsequent movement of the car becomes impossible. In such cases, only an emergency call for a tow truck can help.

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

The main sign of sensor depressurization is loss of power, especially during high-speed movement, characteristic tapping from under the hood while driving, which is accompanied by unpleasant jerks and an unpleasant odor that is emitted from the exhaust. Also, the depressurization is evidenced by the visible sediment of soot formations on the body of the exhaust valves and in the area of ​​\ u200b \ u200bthe candles.

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

Electronic check of lambda probe

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

The device is checked during the full operation of the engine, since at rest the sensor will not be able to fully convey the picture of its performance. In the event 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 repairing from many automotive manufacturers. However, the overestimated cost of such a unit from official dealers discourages any desire to purchase it. The optimal way out of this situation can be a universal sensor, which is much cheaper than its native counterpart and is suitable for almost all car brands. Also, as an alternative, you can purchase a sensor that was in use, but with the duration of the warranty period, or a completely exhaust manifold with a lambda probe installed in it.

However, there are times when the lambda probe functions with a certain error due to severe pollution as a result of the settling of combustion products on it. In order to make sure that this is indeed the case, the sensor must be checked by specialists. After the lambda probe has been checked and the fact of its full operability has been confirmed, it must be removed, cleaned and installed back.

In order to dismantle the oxygen level sensor, it is necessary to warm up its surface to 50 degrees. After removal, the protective cap is removed from it and only after that you can start cleaning. Phosphoric acid is recommended as a highly effective cleaning agent, which easily removes even the most stubborn combustible 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 ensures complete tightness.

It is very difficult, so it needs constant support of its efficiency and timely preventive maintenance. Therefore, in case of suspicion of a malfunction of the lambda probe, it is necessary to immediately diagnose its operability and, if the fact of failure is confirmed, replace the lambda probe. Thus, all the most important functions of 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 vehicle.

The service life of lambda probes under normal operating conditions is from 50 to 250 thousand kilometers, depending on the type of sensor.

The most common causes of their premature failure are listed below.

If an error is detected in the operation of the lambda probe, then it is necessary to conduct a complete external inspection and check its operation:

1. Check the integrity of the electrical connector and sensor wires.
2. Carefully inspect the sensor itself for dents, cracks and other mechanical damage.
3. Check the cleanliness of the contact block of the electrical connector, as well as the absence of traces of corrosion on it.

Typical malfunctions of lambda probes, their causes and remedies

← If the engine is running normally and the fuel burns out completely, then there is no plaque on the working tip of the sensor, and its surface has a dull matte dark gray color.

Poisoning of the sensor's sensing element.

If you observe the following changes on the probe tip, then you should pay attention to the need for additional repair work.

← Antifreeze poisoning. In case of contamination with antifreeze, grainy deposits of gray or greenish color with white streaks appear on the tip:
→ Check the engine cooling system and especially the cylinder head gasket for leaks and repair. Replace the lambda probe.

← Oil poisoning. In case of excessive consumption of oil by the engine, deposits of gray or black color appear on the tip:
→ Check engine for wear or oil leakage and repair. Replace the sensor.

← Soot poisoning. If the ignition and / or fuel system malfunctions, dark brown or black soot appears on the sensor.
→ Check the fuel system, measure the toxicity of the exhaust gases. The sensor will have to be replaced.

← Poisoning with leaded gasoline. One or two fillings with leaded gasoline will result in shiny, dark gray deposits on the sensor.
→ Replace leaded petrol with unleaded petrol and replace the sensor.

← Poisoning with fuel additives. Frequent use of various fuel additives or recent engine overhauls using silicone sealants will result in red or white deposits on the sensor.
→ Clean the fuel system and engine. Replace sensor.

Burnout of the heating element.

If the tip of the sensor looks quite healthy, its wires and electrical connector are in order, then the sensor failed as a result of a burnout of the heating element. The heating element could burn out for the following reasons:

1. Temperature shock as a result of water ingress on the sensor due to the forcing of deep puddles or washing the engine compartment.
2. Faulty electrical wiring.
3. Problems with the catalyst.

→ Attention! If the heating element burns out, the catalyst should be checked, since if the problems with the catalyst persist, the new lambda probe will fail again within a short time.

Corrosion of the contact group of the electrical connector.

Water ingress into the electrical connector (on the contact group) due to the forcing of deep puddles or washing the engine compartment.
→ Try to drive through puddles in a calm mode, without splashes, especially if the car has normal ground clearance.

Mechanical damage to the sensor, sensor cable, electrical connector.

... "Curved" hands of auto mechanics who dismantle / mount the sensor when carrying out other work or parts located near the sensor. Damage occurs as a result of the fall of the sensor on a hard surface, the fall of something hard and heavy (key, head, part, bolt, etc.) onto the sensor or electrical connector.
→ There is hardly any help here, but be careful!

Incorrect laying of the lambda probe cable after re-installation. As a result, the cable insulation melts due to its contact with hot parts of the engine, or, in the case of the second sensor, its breakage during movement.
→ Check the correct wiring after installing the sensor.

This article will talk about what a lambda probe is, we will also consider the symptoms of a malfunction of this node. It is also called an oxygen content sensor. It is installed in the exhaust tract of an automobile internal combustion engine. Moreover, this sensor is installed on both gasoline and diesel engines.

Oxygen Sensor Basics

The lambda probe is similar in its principle of operation to a solid ceramic electrolyte based on zirconium. The ceramics were also alloyed with yttrium oxide. Above is a thin layer of spraying c It turns out that one electrode perceives the exhaust gas, while the other - air from the atmosphere. It is due to this that the parameters of the working gas are compared with normal atmospheric air. It is also worth noting that the most effective work is carried out at temperatures above 300 degrees. It is with this heating that the zirconium electrolyte begins to conduct current. And now it's time to learn about what affects how a lambda probe works. For example, the Priora malfunction symptoms can be determined even by ear.

The principle of operation of the lambda probe

Due to the fact that there is a difference in the mass content of oxygen, an output voltage appears on the sensor electrodes. To increase the sensitivity of the device at low temperatures, for example, when starting the engine, it is necessary to use forced heating. The electric coil is located in the ceramic body of the lambda probe. It has a connection to the vehicle's on-board network. There is also an oxygen sensor element, which is based on It changes its resistance when the engine is running. This is how the lambda probe works. The symptoms of VW Golf 3 malfunction are the same as in domestic cars.

Oxygen sensor operation

At the moment when the engine starts and warms up, the engine operates without data coming from the lambda probe. All correction of the air-fuel mixture is carried out according to data received from other devices. In particular, these are throttle valves, engine temperature, crankshaft speed. The main feature of a zirconium-based lambda probe is that with a slight deviation from the oxygen content norm when analyzing the composition of the fuel mixture, there is a significant change in the output voltage in the range of 0.1-0.9 Volts.

Titanium oxygen sensors

Titanium dioxide sensors are also available. Then, when there is a change in the mass fraction of oxygen in the exhaust gases, they gradually change the resistance in volume. No voltage is generated in sensors of this design. They are much more complicated than zirconium ones, they are used on very expensive cars, for example BMW, Nissan, "Jaguar". Titanium-based devices are usually not used on budget cars, as they are expensive. On cars of the middle and low class, the cheaper zirconium one uses a lambda probe. Signs of malfunction "Renault-Megan 2" shows such that are no different from those present on domestic cars.

Differences between lambda probes

It is worth noting that the principles of operation of oxygen sensors are the same, regardless of who the manufacturer is. The only difference is in the dimensions of the body of these elements. There may also be a slightly different connection, often there is a difference in the connector. All sensors, as mentioned above, are heated or not. Therefore, they differ in the number of wires for connection. According to the materials, the differences are as follows: either zirconium or titanium. In the latter, the heater output is always red. There are also types for diesel engines. They are more broadband. You cannot install such a lambda probe on a gasoline engine. Symptoms of a malfunction (Skoda-Octavia is also of interest to many motorists) are accompanied by an error code with a short description.

Why does the lambda probe fail?

Very often, the cause of premature failure is the poor quality of gasoline. Iron and lead, which can be present in poor gasoline, instantly clog the platinum electrodes. Consequently, the oxygen sensor fails, it cannot normally take all readings. If they have a strong output, then a certain amount of oil will get into. This is also the cause of the premature failure of the oxygen sensor. Even if a little solvent or detergent accidentally gets on the oxygen sensor, you can immediately say that it is broken. He does not survive the ingress of such solutions. The destruction of the lambda probe occurs when pops occur in the exhaust system. Ceramics are very fragile, so sharp impacts like these can destroy them. If the ignition angle is incorrectly set or if the air-fuel mixture is too rich, the sensor housing will heat up strongly. This becomes the cause of premature failure.

Less popular causes of breakage

Please note that when installing the lambda probe, you cannot use various sealants that are based on silicone. You can also destroy the lambda probe if you try to start the engine many times, making short pauses between attempts. Provided the engine will not start. This will inevitably lead to the accumulation of the air-fuel mixture in the exhaust system. After some time, it will ignite and create a powerful blast wave. Even a poor-quality contact or in the output circuit that can destroy the device. The total resource of the elements ranges from 30..70 thousand kilometers. It largely depends on the conditions under which the operation takes place. The longest service life is for sensors with additional heating. Most foreign cars use such a lambda probe design. The symptoms of malfunction ("Ford Focus 2" or "Skoda" are in your possession) are the same. Therefore, you can diagnose yourself if you correctly recognize all the symptoms.

Frequent sensor breakdowns

Among the most popular breakdowns, one can note an inoperative heating element, as well as loss of sensitivity. Due to the latter, the speed of the device decreases. Most importantly, try not to replace the lambda probe with any imitators. The electronic control unit will not be able to recognize someone else's signal. Therefore, the fuel mixture correction for this simulator will not occur. Please note that if the oxygen sensor has successfully worked in the conditions of our country (low-quality gasoline), and its service life is clearly more than three years, then you do not even need to contact the diagnostician. It is immediately necessary to replace the lambda probe. The Skoda clearly shows signs of malfunction when the vehicle has been driven over 70 thousand km. Some models of oxygen sensors may even have a resource of just over 30 thousand kilometers.

How to tell if a sensor is defective

If there is an unstable operation of the motor at low revs, it feels as if the engine is "troit". And at the same time, the consumption of gasoline increases, the dynamics of the car worsens. Often you can hear a crackling noise coming from the catalytic converter after you turn off the engine. It is also possible to increase the (significant) temperature of the catalyst itself. Sometimes it heats up so much that the metal simply heats up. In some vehicles, a malfunction can also be judged by the Check Engine warning light. Only, unfortunately, not all electronic control systems allow you to identify and indicate a malfunction of this element.