Lambda probe: is it necessary, and other questions on the oxygen sensor

Not a single statistical agency undertakes to calculate exactly the total number of cars on an internal combustion engine on a planetary scale. Registration rules vary too much, and many cars remain unaccounted for. But an approximate figure of 1,2 billion units emerges, of which the car fleet is 95%.


Ecologists in their calculations turned out to be more meticulous. They took one average passenger car and proved that in a year it emits 135 kg of carbon monoxide into the atmosphere, not to mention 25 kg of nitrogen oxides, hydrocarbons, benzpyrene, sulfur dioxide, particulate matter. It was the conclusions of scientists that forced manufacturers to install special oxygen sensors (OC) in cars.

The task of the lambda probe

The wheels of the vehicle rotate the crankshaft, which receives energy from the combustion of fuel in the engine cylinders. However, pure gasoline in the combustion chambers will not ignite by moving the pistons: oxygen is needed for the process. It is taken from the ambient air and forms an air-fuel mixture (FA).

For the efficient operation of the internal combustion engine, the latter must have a strict volumetric ratio of oxygen and fuel. The optimal proportion has long been calculated and is 14,7 parts of air to 1 part of fuel: such a mixture is called stoichiometric.


Here we come to the concept of "excess air ratio in fuel assemblies". This parameter is denoted by the Greek letter λ (or more commonly - L), which is read as "lambda". Hence the name of the sensor - lambda probe (LZ). When the air-to-fuel ratio is correct (14,7:1), lambda is equal to one - this is the ideal that is strived for in the automotive industry. That is, at λ=1, the fuel in the chambers burns out completely, which means that a minimum of harmful substances is emitted through the exhaust tract.

Reduces heavy emissions, however, not the sensor itself, but the catalytic converter integrated into the car's exhaust system. In the catalyst, the very excess air that has not completely burned out in the engine cylinders is burnt out.

But the converter cannot function properly and will "die" without constant control of the air-fuel mixture. Just this task is performed by an oxygen concentration sensor - a lambda probe. The "window" of the oxygen controller, and, consequently, the catalytic converter, is very narrow - λ=1±0,01.


Like any sensor, LZ sends real-time signals to the engine ECU about the state of the fuel mixture, or rather, about the percentage of oxygen molecules in the exhaust (normally 0,1-0,3%). The electronic "brain", having analyzed the data, corrects the structure of the fuel assembly, the ignition timing and supplies a balanced combustible mixture to the combustion chambers.

It follows from the foregoing that air sensors can only be installed on cars with electronic (discrete) fuel injection: owners of carburetor engines should not worry about lambda probes. And the owners of injection engines should study the topic at least at a basic level, because at a certain time they will have to change the elements. Often drivers do it with their own hands, since the procedure is simple.

How does a lambda probe work?

In physical terms, the part looks like a cylinder 5-7 cm in size. The LZ is connected to a regular place by wires. The operation of the element is based on the electrochemical principle, which we will consider.


There is a solid electrolyte of zirconium dioxide (or other material) enclosed between two porous platinum-coated electrodes. When the electrolyte is heated as a result of the movement of atmospheric air and exhaust gases, a potential difference arises between the electrodes. Moreover, the voltage on the sensor electrodes depends on the amount of unburned oxygen in the exhaust gases. Considering that the zirconium electrolyte acquires conductivity only when heated to 300-400°C, it makes no sense to measure residual oxygen when it is cold.

Where is DC

We will consider the location of the LZ using the example of the Lada Vesta car. As a rule, two oxygen sensors work in the exhaust manifold of a car with a 2-liter power unit:

✅ Control (upper) sensor. Located under the hood, on top of the exhaust manifold adjacent to the engine. The part is screwed into the threaded hole in front of the catalyst
✅ Diagnostic (lower) controller. Located under the bottom. You can find it on the lower flange of the exhaust tract, that is, after the catalyst. Actually, the diagnostic sensor "reports" to the ECU about the state of the catalyst


In engines with motors over 2 liters, 4 sensors are installed in the same places, but in pairs - on the left and right.

Signs and consequences of a malfunctioning lambda umbrella

First, let's talk about the reasons for the failure of the LZ. The most common:

✅ Depressurization of the exhaust tract
✅ Natural wear or mechanical damage to the element
✅ Short circuit in car wiring
✅ Poor quality fuel additives
✅ Unregulated ignition
✅ Too rich or poor TVS

The sensor fails gradually. At the first stage, idle speed is destabilized. This is followed by a loss of power, the engine reacts poorly to the accelerator pedal, and fuel consumption increases. In addition, the car starts to twitch, pops are heard from under the hood and, finally, the check engine check engine lights up: everything indicates the need to replace the spare part.

Which lambda probe to choose

Breakage or wear of the LZ with the subsequent replacement of the element occurs at 60-130 thousand kilometers. The period depends on the dust content and ambient temperature, the quality of the fuel, driving style and a number of other circumstances.


Having taken care of the problem of choosing a spare part, consider the following options suitable for Lada Vesta:

✅ BOSCH 226A41771RF. Bosch products need no introduction. Products, including oxygen concentration sensors, are known in 150 countries around the world. The original product is distinguished by the KeySecure System sticker, which can be considered a phone through a special application. Price - from 2 rubles.
✅ DENSO DOX0109. The brand's auto components are among the top ten in the world: 90% of cars have at least one part manufactured at DENSO factories. The sensor with catalog number DOX0109 is positioned by the manufacturer as a universal sensor: a connector is included to connect to the original connector. The cost is over 3 thousand rubles.
✅NGK0044. Universal parts of a well-known manufacturer are distinguished by the correct geometry of the electrodes, the quality of the thread, and the good fit of the seal. Electrical appliances from NGK go to car factories for original equipment. On the price tag, the amounts are frightening - up to 8 rubles.

Also, controllers with a long service life are offered by the Czech company Profit. Prices are moderate - from 1 rubles.

Is it possible to disable the lambda probe?

Can. But is it necessary? On this issue, just two opinions of conditional opponents collide: the garage "Uncle Vasya" and the "Certified Auto Mechanic".

The first will "cut to hell without waiting for peritonitis", and will do it in his garage. And the burning Check Engine will be extinguished at the chip studio, where they promise “pleasant bonuses” in the form of increased power, improved traction on bottoms, and reduced fuel and oil consumption. This is at best, at worst - it will corny throw off the power from the annoying light bulb. The ecology of the garage master does not care.


A learned person - a "Certified Auto Mechanic" - will be outraged by the illegal knocking out of the "stuffing" of the catalyst or the complete removal of the spare part along with the lower lambda. The specialist calculated that, firstly, the costs cannot be avoided: a flame arrester should be put in place of the removed part (although many car owners ignore this point), and then they still competently “deceive” the electronics. Secondly, the reduction of oil and fuel consumption must be accompanied by fortunate circumstances. Therefore, the decrease, if any, is most often a miserable 3%.

“Pleasant bonuses,” the law-abiding mechanic assures, absolutely turn into increased noise from under the hood and unpleasant odors in the cabin. Another argument is ecology and legislation. If you close your eyes to both, in the end it will turn out to be more expensive for yourself. If not for you, then for future generations.