Lambda probe is a device that recognizes the composition of exhaust gases in order to control the nature of the conversion of fuel in the engine. This is a multi-component device, its components are made of heat-resistant materials. The device is installed in front of the catalyst exhaust system, and it starts functioning at a high temperature. Sometimes there are two sensors - before and after the catalyst.
As the device heats up, an output voltage appears on its electrodes. Then the lambda probe measures the residual oxygen in the exhaust gases of the car. If its value deviates from the norm, a signal is sent to the ECU, which restores the composition of the fuel-air mixture.
Blende- a detail that complements the device, corrects the signal coming from it. There are two types - mechanical(gas passes through it and oxidizes, the amount of oxygen decreases, the ECU receives a more correct value of the indicator) and electronic(supports the operation of the auto power unit adjustment system, analyzes the actual composition of the exhaust, on the basis of which it corrects the signal supplied by the ECU; as a result, the engine operates normally, despite a faulty catalyst or its absence).
The lambda probe can be narrowband and broadband. In the first case, it is able to analyze only nominal voltage values, which can lead to engine malfunctions due to incorrectly changed fuel concentration in fuel mixture. Wide-band consists of two-point and pumping elements; receives oxygen from the exhaust system under the influence of current; keeps a constant voltage between the electrodes, and if it grows, a signal is sent to the computer; after that, the unit adjusts the composition of the fuel mixture.
Scheme of operation of a narrow-band lambda probe The difference between a broadband probe and a narrowband probe in that it measures the concentration of oxygen in the exhaust gases at any engine speed. Its range is from 0 to 5 volts. In narrowband, it is only 0-1.
Oxygen sensor works on 50000-100000 km of run. If you fill the tank several times low-quality gasoline, the sensor can fail almost immediately.
If the lambda probe heating does not work, the device will not feel problems with the composition of the fuel mixture. And the engine will work with increased load, and the toxicity of exhaust gases will increase dramatically. So is fuel consumption.
Damage consequences: the engine will start to run unstable even at Idling, fuel consumption rises, poor purification of exhaust gases by a catalyst; the car moves jerkily, does not obey well; motor power is reduced.
How to understand that the device is broken: the car in motion starts to twitch; uncharacteristic sounds are heard from under the hood; on the dashboard the indicator is lit; engine power drops, and the accelerator pedal works more slowly; from the exhaust pipe comes a sharp and bad smell; the motor is overheating. With a complete failure of the car, it may not go.
Read more in our article on how the lambda probe works.
Read in this article
What is a lambda probe
AT modern cars a lot of sensors are installed, which not only allow better control of the operation of its various systems, but also increase environmental safety. One of the devices is a lambda probe. The device recognizes the composition of the exhaust gases in order to control the nature of the fuel conversion in the engine.
If the ratio of fuel and air is no longer optimal, the sensor informs the electronic control unit of the injection system. He brings the composition of the mixture back to normal by reducing or increasing the volume of fuel supplied.
How does a lambda probe work in a car
To understand how a lambda probe works in a car, you need to understand what it is made of. This is a multi-component device, its components are made of heat-resistant materials. The device is installed in front of the exhaust system catalyst, and it starts to function at a high temperature. Sometimes there are two sensors - before and after the catalyst.
As the device heats up, an output voltage appears on its electrodes. And the lambda probe acquires the ability to measure the residual oxygen in the exhaust gases of a car. If its value deviates from the norm, a signal is sent to the ECU, which restores the composition of the fuel-air mixture.
What is a scam and why is it needed?
One of the breakdowns may affect the exhaust system catalyst, after which the exhaust gas emission increases. It can be removed or replaced with a flame arrester. But the engine starts emergency mode due to an incorrect lambda probe signal.
A cheat can save you from this. The part complements the device, corrects the signal coming from it. There are two types of cheats:
- Mechanical. The gas passes through such a part and is oxidized. As a result, the volume of oxygen decreases, the ECU receives a more correct value of the indicator. The system is given information in the form in which it occurs with a properly functioning catalyst.
- Electronic. This is a more complex device based on a microprocessor. This is how the snag of an electronic type lambda probe works: it supports the operation of the auto power unit adjustment system, analyzes the actual composition of the exhaust, on the basis of which it corrects the signal supplied by the ECU. As a result, the engine operates normally, despite a faulty catalyst or its absence.
Scheme for connecting electronic snag What does broadband mean
Devices are narrowband and broadband. In the first case, they are able to analyze only nominal voltage values. That is, information transmitted at low engine speeds. Everything else reads with an error, and the computer receives a not quite correct signal. This can lead to engine malfunctions due to incorrectly changed fuel concentration in the fuel mixture.
How a broadband lambda probe works:
- consists of two-point and pumping elements;
- thanks to this structure, it receives oxygen from the exhaust system under the influence of current;
- keeps a constant voltage between the electrodes, and if it grows, a signal is sent to the computer;
- after that, the unit adjusts the composition of the fuel mixture.
Scheme of operation of a broadband oxygen sensor The difference of the broadband probe is that it measures the oxygen concentration in the exhaust gases at any engine speed. Its range is from 0 to 5 volts. In narrowband, it is only 0-1.
Does the lambda probe work without a catalyst
The failure of the exhaust system catalyst (exhaust gas purifier) is one of the common problems, causing difficulties with the operation of the engine. This happens if there are two controlling sensors: one is installed in front of the device, and the other after it.
In this case, the oxygen content in the exhaust passing through the catalyst will change. This will detect the sensor behind it. He will transmit a false signal to the ECU about the need to correct the composition of the fuel mixture. And in this case, the answer to the question of whether the lambda probe works without a catalyst is negative. After all, he gives a signal based on distorted information. Here you need to put a trick.
Another option is to flash the “brains” of the car, change the catalyst to a flame arrester and remove the sensor. Otherwise, problems with injection will begin, which can lead to high consumption of gasoline, increased engine load, and breakdown.
The oxygen sensor in some cars is located just in front of the catalyst. Then the lambda probe analyzes the exhaust gases that have not yet passed through the cleaner. That is, the data is not distorted whether the catalyst works or not. With a breakdown of the cleaner, only the amount of toxic gases from the exhaust pipe increases.
How much work in general
The oxygen sensor is one of the most sensitive parts of the car. It is enough for 50,000-100,000 km of run. But how long a lambda probe works also depends on:
- car operating conditions;
- engine health;
- type of device (unheated, heated, glider);
- fuel quality.
The last factor is especially important. If you pour low-quality gasoline into the tank several times, the sensor may fail almost immediately.
Watch this video on how the lambda probe works:
If the heating does not work
The oxygen sensor begins to analyze the composition of the exhaust after it warms up to 300-400 degrees. If the lambda probe heating does not work, the device will not feel problems with the composition of the fuel mixture. And the engine will work with increased load, and the toxicity of exhaust gases will increase dramatically. So is fuel consumption.
The only way out will be to replace the sensor completely or remove it along with the firmware of the “brain” of the machine.
The consequences of a breakdown
A malfunctioning oxygen sensor will have a detrimental effect primarily on the engine. It will start to function unstably even at idle. When the lambda probe does not work, the consequences are as follows:
Engine power drops, and the accelerator pedal, when exposed to it, works more slowly;
From these changes, it is not difficult to understand how a faulty lambda probe works. If it is completely out of order, the car may not go. When the sensor is depressurized, the “brain” of the machine receives many signals about problems, and the injection control system is blocked.
If we talk briefly about how the lambda probe works, it keeps the engine running longer, saves fuel, and reduces exhaust toxicity. It is necessary to regularly check it with a specialist, monitor the quality of the fuel and the engine cooling system. And if the sensor fails, be sure to change it.
Useful video
Watch this video on how to properly check the lambda probe:
Didn't find an answer to your question? Find out, how to solve exactly your problem - call right now by phone:
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, knowing the symptoms of a lambda probe malfunction will help determine the cause of the problem.
[ Hide ]
Description of the device and location
With the advent of electronic gasoline injection systems, designers faced the task of adjusting the composition of the fuel mixture. For this they began to be used. The devices maintain the composition of the fuel mixture within certain limits, which allows for maximum efficiency. catalytic converter. With other compositions of the mixture, the neutralizer starts to work incorrectly and fails.
Depending on the design of the exhaust system, one or two sensors are used:
- 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.
- With the introduction of Euro-3 standards, a second probe began to be used, located after the neutralizer. analyzes data from two probes and indirectly evaluates the efficiency of the catalyst, and also corrects the composition of the mixture.
Manufacturers have set a service life for products:
- probe without heating coil - no more than 80 thousand km;
- heated unit - up to 100 thousand km;
- planar (broadband) probes - up to 160 thousand km.
The stated life of the probes is not accurate. The service life of devices depends on many factors and may be less or more than the specified values.
Device diagram
Let's consider a probe diagram that gives an idea of the placement of nodes. Knowledge of the design allows you to understand the location of parts prone to breakage.
Probe design example The design includes:
- 1 - a metal fitting designed to install the probe, there are turnkey edges on the outer surface, a thread is located below;
- 2 – ceramic insulator;
- 3 – a sealing element for input of a plait of wires;
- 4 - signal wires;
- 5 - a metal protective cap equipped with ventilation products is designed to protect the measuring element from damage;
- 6 - spring contact part;
- 7 – sensitive element made of ceramics;
- 8 - heating rod;
- 9 - ventilation channel;
- 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 work and floating revolutions at idle or low shaft speed;
- reduction of accelerating parameters of the car;
- noticeable (sometimes by several liters) increase in fuel consumption;
- turning on the indicator check engine and the appearance of errors in the memory of the control unit.
Causes of a malfunctioning 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 test an oxygen sensor?
If any of the above problems occur, check the condition of the oxygen sensor. Checking the lambda probe is carried out visually and using electronic equipment.
visual inspection
The very first stage of verification is an external inspection of the part, which consists of the following steps:
- Perform a visual inspection of wiring and plugs. Melting of insulation, mechanical damage, oxidation of contacts are unacceptable.
- The working surface of the sensor must be free of soot and soot deposits. A layer of soot occurs when worn piston rings or poor valve tightness. Soot changes the sensitivity of the probe, which sends incorrect information to the engine control unit. After cleaning the part, performance is restored. Cleaning is done with a soft brush and soaking the probe in phosphoric acid for 15-20 minutes.
- If deposits of white or light gray color are present on the surface of the sensitive element, then this indicates the use of fuel with additives based on tetraethyl lead. As a rule, such a sensor quickly fails.
An external examination 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
In the device, the heating circuits may burn out or the destruction of the working element may begin. These faults can be detected using electronic test instruments.
There are three types of lambda probe plugs:
- two-wire (grounding and signal);
- three-wire (a positive power wire for the heating element is added);
- four-wire (there is an additional grounding of the heating coil).
To perform a lambda probe test, factory documentation is required to determine the purpose of the wires and a digital multimeter switched to voltmeter and ohmmeter mode.
Approximate sequence of actions:
- Warm up the engine to operating temperature, because only in this case it is possible to obtain correct data.
- Ring the 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. The resistance is measured by connecting to two pins in the plug (for a four-wire probe) or to a heater pin and the car body (in a three-wire probe). If the resistance is zero, this means that a short circuit of the heating element windings has been detected. The desire of resistance to infinity is a symptom of a break in nichrome heating filaments.
- Ring the wiring going to the heater from the control unit for breaks.
- Check the voltage in the signal circuit. The negative signal can be taken from the car body or directly from the battery terminal. Before checking, the engine should run at medium speed (2500-3000 rpm) for 2-3 minutes. Disconnect the plug and connect the test device.
- Bring the speed to 2500-2600 rpm and abruptly throw 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 per second).
- Disconnect the vacuum tube from the pressure regulator to check the degree of lean mixture. It is possible to force the mixture to become leaner by closing the air intake of the throttle assembly by hand. Measure the voltage, which should be within 0.2 volts or less.
- Put the tube back.
- Sharply increase the speed 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 depending on the mode of operation and the composition of the mixture. However, a thorough check with an oscilloscope or a test computer is recommended to confirm the failure.
Checking with an oscilloscope
The advantage of checking the probe with an oscilloscope is the ability to control not only the voltage value, but also the amplitude of the change over time. Shifts in the amplitude characteristics within small limits cause a change in the parameters of the engine, but are not registered by the control unit as an error. Checking with an oscilloscope is carried out in the conditions of a specialized service, since the device is rarely found in personal possession.
Sequencing:
- Warm up the engine.
- Connect the oscilloscope leads to the sensor.
- Carry out an idle test. Below are sample curves taken with an oscilloscope. By the amplitude of the signal, one can draw a conclusion about the state of the part.
- Replace damaged part and retest.
How to Check the Sensor with ELM327 USB OBD II Scanner
The owner can independently test the sensor using an ELM327 scanner that works according to the OBD II protocol. The device is compatible with most cars of Russian and foreign production.
Test sequence:
- Connect the tester to the diagnostic socket. The location of the connector must be specified in the documentation supplied with the vehicle.
- Read the operating parameters and transfer them to a laptop with pre-installed special software. The most common utility is Torque Pro, which is in the public domain.
Below is a video tutorial on the operation of the ELM327 scanner with the Torque Pro utility, provided by the Savontiy channel.
Instructions for replacing the sensor with your own hands
Before starting work, it is required to prepare materials and tools:
- New probe.
- A wrench or nozzle that will allow you to unscrew the sensor housing from the manifold. On some vehicles, you can try to remove the device with a regular 22 mm open-end wrench or a gas adjustable wrench. But most of the machines require the use of a specialized nozzle.
- Nozzle extension.
- Torque wrench up to 50-100 N/m.
- Protective gloves and sleeves, as work is carried out on a heated collector.
- Wrenches for dismantling the protective heat shields and/or manifold.
Lambda probes should be changed to the same model or a similar one that is suitable in terms of parameters. You can not install the first sensor that comes across. Before installation, carefully read the instructions supplied by the manufacturer.
Approximate sequence of actions when replacing the first probe:
- warm up power unit up to operating temperature. In this case, thermal expansion of the exhaust system elements occurs, which makes it easier to unscrew the sensor from the manifold or exhaust pipe.
- Turn off the engine.
- Remove the terminal from the battery to prevent the possibility of starting the electric cooling fan.
- Carefully disconnect the probe connector from the wiring.
- Put on protective gloves and remove the probe wire from the clips.
- 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 out rust. After that, you should try to pull the probe from its place, if the part does not start to unscrew, repeat the warm-up again.
- Wipe the installation site from the remnants of the old graphite grease.
- Check for proper grease on the threads of the new probe. The tool may be included in the delivery in a separate bag. The lubricant is applied in a thin even layer to the thread. Application to the protective cap is strictly prohibited, as this leads to the formation of hard deposits and deterioration of the probe operation parameters. If the car uses a sensor fixed with two bolts, then they do not need to be lubricated.
- Carefully screw the sensor into place by hand until it stops.
- Tighten the probe with a wrench to the required torque. Most manufacturers indicate a force of 40-45 N / m, but it is recommended to clarify the value in the service literature. In the absence of a torque wrench, tightening is done by turning the probe 180º after tightening by hand until it stops.
- Route the harness along the clamps, secure with clamps if necessary.
- Connect the battery and remove the errors from the control unit. Errors are removed using a computer or otherwise (depending on the make and model of the car).
When installing the probe, the tightening torque must be observed. Exceeding the force leads to the destruction of the probe body or stripping of the thread, low torque causes the breakthrough of exhaust gases and uneven heating of the part.
How to repair a lambda probe?
Manufacturers of lambda probes position the parts as non-separable and beyond repair. However, some car owners, with some success, try to disassemble and repair the sensors, assembling one workable device from two or more damaged devices.
The car owner should remember that such a lambda probe repair is a temporary measure. Recommended to purchase new sensor, and refurbished to use as a spare.
Heating element repair
An approximate sequence for disassembling and repairing a sensor with a damaged heating element:
- Carefully cut the outer casing of the sensor.
- The second sensor is cut in the same way.
- Remove the heating rods from the sawn bodies. The whole device must be wiped from soot and dirt with a dry cloth. The use of cleaning agents is not recommended as the heater may be damaged by chemical reactions.
- Install the heater in the probe to be applied on the vehicle.
- Solder the case with copper-phosphorus solder having a melting point of about 700 ºС. A gas jewelry burner is used as a heat source.
- Check the performance of the product with a tester and install the probe into the manifold. If the repaired device does not work, you can try to change the heater again. Below are photos showing 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 idea of the authors, the resulting resistance should give the correct signal to the control unit and turn off error information. In fact, this is what happens, but the life of additional resistance is from several hours to several days. heating up high temperatures resistor can cause a fire in the engine compartment.
Troubleshooting a broken wiring harness can be done as follows:
- Saw through the housing on the top of the probe.
- Dismantle completely old wires, as the insulation wears out and cracks over time.
- Remove pins with soldered wires from the donor block. Any available plug-in block can be used as a donor.
- For further work, it is necessary to unsolder the connecting elements from the pins.
- Assemble a new wiring harness using the stock rubber seal from the probe.
- Install the removed connectors on the ends of the wires.
- Connect the wiring to the mating cables of the lambda probe.
- Crimp the contacts and additionally solder with refractory copper-phosphorus solder.
- Solder the case and coat the place where the wire harness is inserted into the sensor with a heat-resistant sealant.
Cleaning from soot and soot
Another repair option is to clean the measuring element from soot and soot:
- Carefully cut off the protective caps.
- Soak the sensor in phosphoric acid, then carefully clean off the carbon deposits with a brush. It is not recommended to apply force, since the measuring element is extremely fragile.
- If necessary, clean the element further by heating it on a gas burner. The procedure should be performed carefully, as cracking of the part is possible. Heating and cooling with cold water recommended in a number of sources is prohibited, since this will lead to the complete failure of the probe.
- 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 reference prices for devices used on some car models.
Video “Checking the lambda probe”
The lambda probe is one of the elements of the injection car power system, which can create problems in our operating conditions. How to avoid them?
Purpose
The Greek lambda in the automotive industry refers to the ratio of excess air in the air-fuel mixture. Hence the name of the sensor that measures this coefficient, or rather, the residual oxygen (O2) in the exhaust gases (another name is the oxygen sensor). The purpose of the sensor is to provide the engine ECU with information to determine the nature of the fuel combustion. This is necessary to create normal operating conditions for the catalytic converter. The fact is that the "window" of the effective operation of the catalyst is very narrow, when 14.6-14.8 parts of air and 1 part of fuel are burned in the cylinders (when such a mixture is burned, lambda \u003d 1 ± 0.01). This precise air-fuel mixture control is only possible with electronic fuel injection power systems. The lambda probe in these systems performs the function of a controller in the exhaust tract.
Lambda probe: causes and symptoms of breakdowns
Malfunctions or even failure of the lambda probe can occur due to:
| breaks in electrical connection circuits; | |
| closures; | |
| pollution by combustion products of gasoline with a high content of octane-boosting additives; | |
| thermal overload due to misfiring; | |
| mechanical damage (for example, when driving off-road). |
Significantly reduce the life of the lambda probe poor condition oil scraper rings, antifreeze ingress into cylinders and exhaust pipes, enriched air-fuel mixture.
With a faulty lambda probe, the CO content in the exhaust increases from 0.1-0.3% to 3-7%. It is difficult to reduce its value in most older motors without replacing the sensor, since the power reserve of the potentiometer mixture quality controller may not be enough. In vehicles with two lambda probes, in the event of a failure of the second sensor, achieve normal operation engine without serious intervention in the electronics is impossible.
Lambda probe: malfunction treatment
There is no technology for repairing faulty lambda probes - in the event of a breakdown, they must be replaced. However, our "Uncle Vasya" nevertheless developed a method for restoring these sensors, but it is not effective in all cases. Most often, it stops working due to carbon deposits on the sensitive element under the protective cap. If the plaque is removed, the lambda's performance is restored. You can clean the sensitive element of the sensor by washing it in phosphoric acid, which corrodes impurities in 10-20 minutes without destroying the electrodes with rare earth metals. It is more efficient to clean the lambda probe after removing the protective cap on lathe and washing with a thin brush. But it is advisable to do this if it is possible to fix the cap using argon welding. After washing, the sensor should be rinsed with water and dried. If washing does not help, then the “lambda” needs to be changed. The cost of washing is much less than the cost of a new lambda probe (from UAH 300). It is possible to replace an unheated sensor with a heated one (but not vice versa!). If the connectors are incompatible, lay the missing heating circuit yourself, and use universal automotive contacts instead of the connector.
|
|
Lambda probe: diagnostics
Effective measurement of residual oxygen in the exhaust gases lambda probe provides after heating to a temperature of 300-400°C. Only under such conditions does the zirconium electrolyte acquire conductivity, and the difference in the amount of atmospheric oxygen and oxygen in the exhaust pipe leads to the appearance of an output voltage on the electrodes of the lambda probe. Therefore, the lambda probe signal is checked with the engine running and warm. For measurement, an oscilloscope is better suited than a multimeter, since it most accurately evaluates the shape and frequency of the signal.
Then the resistance of the sensor heater is measured (with the plug disconnected), which is at room temperature from 2 to 14 ohms (according to the manufacturer's requirements). Next, the voltage supplied to the heater is checked: with the ignition on and the probe connector connected, it should be at least 10.5 V. If this value is lower, the battery voltage, cables and connections must be carefully checked.
Lambda probe: installation subtleties
| Sensors must only be installed and removed using the appropriate tools. | |
| If the lambda probe is reused, the thread must be treated with a special mounting paste. When doing this, avoid getting paste on the protective tube, as this can lead to malfunctions of the sensor. New lambda probes from leading manufacturers are pre-treated with paste. | |
| Observe the tightening torque specified by the manufacturer, which is usually between 40 and 60 Nm. | |
| Lambda probes must be handled with care to avoid mechanical damage (eg due to falling). | |
| Because the sensors draw outside (reference, for comparison) air through the connector, it cannot be treated with contact spray or lubricant. When flushing the engine and bottom, the lambda probe connector should be carefully insulated. |
|
||||||
Yuri Datsyk
Photo Bosch, GM
If you find an error, please highlight a piece of text and click Ctrl+Enter.
Unfortunately, not all car owners know what a lambda probe is and why it is needed. The lambda probe is an oxygen sensor that allows electronic system control and balance the correct ratio of air and gasoline in the combustion chambers. It is able to correct the structure of the fuel mixture in a timely manner and prevent 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 check of the lambda probe will guarantee the stable operation of the car 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 indicator should range from 0.1 to 0.3 percent. Uncontrolled excess of this standard value can lead to unpleasant consequences.
With a standard assembly of a car, a lambda probe is mounted in the exhaust manifold in the area of \u200b\u200bthe connection of the nozzles, however, sometimes there are other variations in 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 layout and a broadband type. The first type is most often found on old cars manufactured in the 80s, as well as on new economy class models. The broadband type sensor is inherent modern cars 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 hard work of such sensors, the working life of the car is significantly increased, fuel consumption and increases the stability of holding idle speed.
From the point of view of the electrical side, it is worth noting that the oxygen sensor is not able to create a homogeneous 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 go through. Thus, we can say that the lambda probe reacts rather to the destabilization of the engine, about which it subsequently notifies the central unit and takes appropriate measures.
The main symptoms of a malfunction of the lambda probe
The main sign of a malfunction of the lambda probe is a change in the operation of the engine, since after its breakdown, the quality of the fuel mixture supplied to the combustion chamber deteriorates significantly. The fuel mixture, in fact, remains uncontrolled, which is unacceptable.
The reason for the exit from the working state of the lambda probe may be the following:
- housing depressurization;
- penetration of external 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 incorrect operation of the vehicle.
In all of the above cases, except for the last one, failure occurs gradually. Therefore, those car owners who do not know how to check the lambda probe and where it is located at all, most likely, will not immediately notice the malfunction. However, for experienced drivers, determining the cause of a change in engine operation is not difficult.
The gradual failure of the lambda probe can be divided 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 fairly wide 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 pops that are uncharacteristic of the engine operation, and a warning light on the instrument panel lights up. All these anomalous phenomena signal to the car owner that the lambda probe is not working properly.
At the second stage, the sensor completely stops working on an unheated engine, while the car will signal the driver about the problem in all possible ways. In particular, there will be a noticeable drop in power, slow response when exposed to the accelerator pedal 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 for a lambda probe failure is engine overheating.
If all previous signals indicating a deterioration in the state of the lambda probe are completely ignored, its breakdown is inevitable, which will cause a large number of problems. First of all, the possibility of natural movement will suffer, fuel consumption will also increase significantly and an unpleasant pungent odor will appear with a pronounced shade of toxicity from the exhaust pipe. In modern automated vehicles, in the event of a breakdown of the oxygen sensor, an emergency lock can simply be activated, as a result of which the subsequent movement of the car becomes impossible. In such cases, only an emergency tow truck call can help.
However, the worst case scenario is the depressurization of the sensor, since in this case the movement of the car becomes impossible due to the high probability of engine failure and subsequent costly repairs. During depressurization, exhaust gases instead of exiting through exhaust pipe, fall into the intake channel of atmospheric reference air. During engine braking, the lambda probe begins to detect an excess of oxygen molecules and urgently delivers a large number of negative signals, which completely disables the injection control system.
The main sign of sensor depressurization is a loss of power, especially felt during high-speed traffic, a characteristic tapping from under the hood while driving, which is accompanied by unpleasant jerks and an unpleasant smell that is emitted from the exhaust. Also, depressurization is evidenced by a visible sediment of soot formations on the exhaust valve body and in the area of \u200b\u200bthe candles.
How to determine the malfunction of the lambda probe is described in the video:
Electronic check of a 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 refute the fact of its failure.
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 case of even a slight deviation from the norm, it is recommended to replace the lambda probe.
Replacing the lambda probe
In most cases, a part such as a lambda probe cannot be repaired, as evidenced by the claims of the impossibility of making repairs from many automobile manufacturers. However, the overestimated cost of such a node official dealers discourages any desire to acquire it. The best way out of this situation can be a universal sensor, which is much cheaper than its native counterpart and is suitable for almost everyone car brands. Also, as an alternative, you can purchase a used sensor, but with a longer warranty period, or completely an exhaust manifold with a lambda probe installed in it.
However, there are cases when the lambda probe functions with a certain error due to heavy pollution as a result of deposition 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 performance 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. Orthophosphoric acid is recommended as a highly effective cleaning agent, which easily copes with even the most persistent combustible deposits. At the end of the soaking procedure, the lambda probe is rinsed in clean water, dried thoroughly and installed in place. In this case, do not forget about lubricating the threads with a special sealant, which will ensure complete tightness.
It is very complex, so it needs constant support for performance and timely preventive maintenance. Therefore, in case of suspicion of a malfunction of the lambda probe, it is necessary to immediately diagnose its performance and, if the fact of failure is confirmed, replace the lambda probe. So everything essential functions of the vehicle will be kept at the same level, which will guarantee the absence of further problems with the engine and other important elements of the car.
First things first when out of order and labda malfunctions in the behavior of the car there are several tangible consequences:
- Unstable operation of the car engine (jerks)
- The work of the catalyst is disrupted (toxicity increases)
Then, to check the lambda probe, you can first unscrew and conduct a visual check (just as it can tell a lot).
Several types of lambdas are installed on cars, sensors can be with one, 2, 3, 4 or even five wires, but it is worth remembering that in any of the options one of them is signal (often black), and the rest are designed for heater (usually they are white).
What and how can I check the lambda
To check, you will need a digital voltmeter (preferably an analog voltmeter, since it has a much shorter “sampling” time than a digital one) and an oscilloscope, if possible, the measurements will be more accurate. Before checking, you should warm up the car because the lambda works correctly at temperatures above 300C °.
First, we are looking for a heating wire:
We start the engine, do not disconnect the lambda connector. The negative probe of the voltmeter (usual tseshka) is connected to the car body. With the plus probe of the shop, we “poke” on each contact of the wire and observe the reading of the voltmeter. When a positive wire of the heater is detected, the voltmeter should show constant 12 V. Next, using the negative probe of the voltmeter, we try to find the negative wire of the heater. We turn on the remaining contacts of the sensor connector. When a negative contact is detected, again, the voltmeter will show 12 V. The remaining wire, signal wires.
Checking the lambda probe with a tester
We take an electronic constant voltage millivoltmeter and connect it in parallel with the LZ (“+” “-” to the LZ, - to the ground), and the lambda probe must be connected to the controller.
When the engine warms up (5-10 minutes), then you need to look at the voltmeter needle. It should periodically go between 0.2 and 0.8 V (i.e. 200 and 800 mV, moreover, if less than 8 cycles occur in 10 seconds, it’s time to change the LZ. Also to be replaced if the voltage “stands” at 0 .45 V.
When the voltage is 0.2 or 0.9 V all the time - something with injection - the mixture is too lean or too rich. Since the voltage of the oxygen sensor should change all the time and jump from ≈0.2 to 0.9V.
There is another fast lambda probe test method. It should be done like this:
It is carefully pierced with the positive contact of the tester (black lambda wire), the other contact is to ground. On a running motor, the readings should fluctuate from 0.1 to 0.9V. Constant readings (for example, all the time 0.2) or readings that go beyond these limits, or fluctuations with a smaller amplitude, indicate a malfunction of the probe.
Exceptions:
- all the time 0.1 - little oxygen
- all the time 0.9 - a lot of oxygen
- The probe is OK, the problem is something else.
If you have time and desire to bother, you can conduct several tests for a rich and lean mixture and additionally.
- Disconnect the oxygen sensor from the block and connect it to a digital voltmeter. Start the car, and by pressing the gas pedal, increase the engine speed to 2500 rpm. Using an enricher, reduce the rpm to 200 rpm.
- Provided that your vehicle is equipped fuel system With electronic control, remove the vacuum tube from the fuel pressure regulator. Look at the voltmeter readings. If the arrow of the device approaches 0.9 V, then the lambda probe is in working condition. The lack of reaction of the voltmeter testifies to it, and its readings are within the lower mark of 0.8 V.
- Do a lean mixture test. To do this, take a vacuum tube and provoke an air leak. If the oxygen sensor is OK, the reading digital voltmeter will be at a level of 0.2 V and below.
- Check the operation of the lambda probe in dynamics. To do this, connect the sensor to the connector of the fuel supply system, and install a voltmeter in parallel with it. Increase engine speed to 1500 rpm. The voltmeter readings with a working sensor should be at the level of 0.5 V. Another value indicates the failure of the lambda probe.
Checking the voltage in the heating circuit
A voltmeter is needed to check for voltage in the circuit. We turn on the ignition and connect it with probes to the heater wires (you cannot disconnect the connector, it is better to pierce it with sharp needles). Their voltage should be equal to what the battery gives out when the engine is not running (about 12V).
If there is no plus, you need to go through the battery-fuse-sensor circuit, since it always goes directly, but the minus comes from the computer, so if there is no minus, we look at the circuit to the block.
Checking the lambda probe heater
In addition to measuring the voltage with a multimeter, you can also measure the resistance to check the health of the heater (two white wires), but you will need to switch the tester to Ohms. The documentation for a particular sensor must indicate the nominal resistance (usually it is about 2-10 ohms), your task is only to check it and draw a conclusion. The video shows this method:
Checking the reference voltage of the oxygen sensor
We switch the tester to the voltmeter mode, then, turning on the ignition, we measure the voltage between the signal and the ground wire. In most cases, the reference voltage of the lambda probe should be 0.45V.
