Oxygen Sensor Function

Oxygen Sensor Function

Date:May 26, 2020

Oxygen sensor: A detailed guide to the working principle and function of the oxygen sensor


What is an oxygen sensor?

An oxygen sensor (commonly referred to as the "O2 sensor" because O2 is the chemical formula for oxygen) is attached to the vehicle's exhaust manifold to show how much oxygen remains in the exhaust as it leaves the engine. To monitor


Where is the oxygen sensor?

The number of oxygen sensors in the vehicle is different. All cars produced after 1996 require oxygen sensors upstream and downstream of each catalytic converter. Therefore, while most vehicles have two oxygen sensors, V6 and V8 engines with dual exhaust have four oxygen sensors upstream and downstream of the catalytic converter in each row of the engine.


What does the oxygen sensor do?

The oxygen sensor produces a unique voltage that operates at high temperatures (approximately 600 ° F). The tip of the oxygen sensor inserted in the exhaust manifold is a zirconium ceramic valve. The inside and outside of the bulb is coated with a layer of porous platinum used as an electrode. The inside of the bulb is vented to the outside air through the inside of the sensor body. When the outside of the valve is exposed to the hot gases in the exhaust, a voltage will flow through the valve due to the difference in oxygen content between the valve inside the sensor and the ambient air. When the fuel is lean (not enough fuel in the mixture), the voltage is relatively low, about 0.1 volt. If the fuel ratio is high (too much mixture), the voltage is relatively high, about 0.9 volts. If the mixture ratio of air and fuel is a stoichiometric ratio (air 14.7 to fuel 14.7),


Upstream oxygen sensor (oxygen sensor 1)

The oxygen sensor 1 is an upstream oxygen sensor associated with a catalytic converter. It measures the air-fuel ratio of the exhaust gas from the exhaust manifold and sends high and low pressure signals to the powertrain control module to condition the mixture. When the powertrain control module receives a low voltage (lean) signal, it compensates by increasing the fuel content of the mixture. When the powertrain control module receives a high voltage (rich) signal, it thins the mixture by reducing the amount of fuel added to the mixture. The process by which the powertrain control module uses the input of the oxygen sensor to condition the fuel mixture is called the closed feedback control loop. This closed-loop operation creates a constant trigger between concentrations, which helps the catalytic converter to minimize emissions by keeping the overall average ratio of the fuel mixture in proper balance. However, if the cold engine starts or the oxygen sensor fails, the powertrain control module goes into open loop operation. In open loop operation, the powertrain control module receives no signal from the oxygen sensor, but orders a fixed rich mixture. Open-loop operation increases fuel consumption and emissions. Many new oxygen sensors have heating elements that help them reach operating temperature quickly to minimize the time spent in open loop work. The powertrain control module goes into open loop operation. In open loop operation, the powertrain control module receives no signal from the oxygen sensor, but orders a fixed rich mixture. Open-loop operation increases fuel consumption and emissions. Many new oxygen sensors have heating elements that help them reach operating temperature quickly to minimize the time spent in open loop work. The powertrain control module goes into open loop operation. In open loop operation, the powertrain control module receives no signal from the oxygen sensor, but orders a fixed rich mixture. Open-loop operation increases fuel consumption and emissions. Many new oxygen sensors have heating elements that help them reach their operating temperature quickly to minimize the time spent on open loop work.


Downstream oxygen sensor (oxygen sensor 2)

The oxygen sensor 2 is a downstream oxygen sensor associated with the catalytic converter. The air-fuel ratio of the catalytic converter is measured to ensure normal operation of the catalytic converter. The role of the catalytic converter is to maintain a stoichiometric air / fuel ratio of 14.7: 1. The powertrain control module, on the other hand, continuously switches between rich and lean mixing with input from the upstream oxygen sensor (sensor 1). Therefore, the downstream oxygen sensor (Sensor 2) should produce a stable voltage of approximately 0.45 volts.


  

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