POST UPDATED IN May, 2023
Oxygen Sensor (O2)
The Oxygen Sensor (also known as lambda sensor) is an automotive component that started being implemented in vehicles in 1980. It is part of the emission control system components. If you are interested in finding out how it works and its importance for the vehicle, below we tell you everything you need to know about the O2 sensor. We will also help you identify its physical characteristics and possible failures.
It is an electronic sensing component. As we mentioned above, it is known as a lambda sensor. It is a rigid element since its shape is that of a small and short cylinder made of an element called zirconium and coated in ceramic so that it can withstand the temperature.
Some oxygen sensors have a small metal casing as protection and this has several lines of perforations for the combustion gases to enter through them.
The O2 sensor performs the basic function of informing the ECU of the amount of oxygen in the gases expelled by the running engine. Its purpose is to achieve efficient fuel consumption and release the least amount of harmful gases into the environment.
To understand how the O2 Sensor works, you must first understand how the combustion process occurs. In order to burn the fuel inside the engine, a spark must be generated, which originates in the spark plugs by voltage from the coil. Air flows into the chamber of each cylinder through the intake valve. If there is air, oxygen is present.
Already there the atmosphere for the controlled explosion is created, fuel injection, air-oxygen, and spark. When this mixture is activated, combustion is generated, which in turn creates the gases that are expelled through the exhaust valves. They pass into the exhaust manifold and are detected by the oxygen sensor on their way through the exhaust pipe.
The gases cause a chemical reaction when in contact with the O2 Sensor. This reaction generates a voltage that travels to the vehicle’s ECU and indicates the quality of the fuel mixture. From there, it will maintain or correct parameters such as fuel injection and air intake.
Although in physical appearance they are all very similar, at least some differences can be found in oxygen sensors. Perhaps the most notable is the wiring or the connection pins.
Some O2 sensors have 2, 3, or even 4 pins, which in turn will be shown in the output branch diagram.
The classification of such sensors is given by the process itself to initiate its function.
The most frequent failure is related mainly to the fuel mixture. For example, if there is little air or oxygen in the mixture, there will be an excess of unburned fuel at ignition. This condition is known as a rich mixture, and it is very harmful because there will be more polluting gases.
If it is the opposite, less fuel injection and more air, the mixture is defined as lean, affecting engine performance.
There are other common failures due to the position where the Oxygen Sensor is located and associated with high temperature, for example:
The O2 sensor has a strong impact on the fuel injection system. In addition to how it regulates the air intake to the engine. Of course, it achieves this by transmitting the corresponding electrical signals to the ECU.
Depending on the amount of oxygen in the exhaust gases, the ECU will adjust the fuel injection timing. This process is continuous thanks to the Oxygen Sensor.
The symptoms are defined, although they can also affect other sensors. If this sensor fails, you will notice the following symptoms:
To check the operation of the O2 sensor of a cable, the method is quite basic, either referred to in bank 1, or bank 1 sensor 2 with a double sensor.
When scanning the sensor you may see the following codes, which have the following meanings:
Cleaning the sensor is very easy and you can do it yourself. Have some thinner or carburetor cleaner handy.
It is important to maintain or replace the Oxygen Sensor at least every 40,000 to 50,000 kilometers.
To know its location look at the exhaust pipe, specifically at the engine outlet, you will find it after the exhaust manifold. There are vehicles of modern automotive technology, to which the manufacturers have integrated two oxygen sensor units. They place one at the exhaust manifold outlet and the other where the catalytic converter goes. This allows them to measure the total efficiency of the emissions system. You can find out the exact location of the O2 sensor by acquiring the car’s electrical diagrams.