What Is Oxygen Sensor In A Car, How It Works, & Construction

What Is Oxygen Sensor In A Car

If you own a car or are planning to buy one, it is important to know what an oxygen sensor is and what it does. An oxygen sensor is a vital part of a car’s emissions control system. It helps to ensure that the car’s engine is running as efficiently as possible and that the exhaust gases are clean.

The oxygen sensor, also known as the O2 sensor, is a part of the exhaust system. Cars produced after 1980, have an oxygen sensor. These sensors provide data to the engine control module to regulate the air-fuel ratio.

You will learn everything about what the oxygen sensor is in a car, its working, construction explained in easy-to-understand language.

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What Is An Oxygen Sensor In A Car

What Is Oxygen Sensor In A Car
What Is Oxygen Sensor In A Car

An oxygen sensor also called O2 Sensor or lambda sensor (λ) is an electronic sensor that monitors how much-unburned oxygen is present in the exhaust gas in the exhaust manifold after the combustion. It measures the oxygen concentration (amount of oxygen) in the exhaust gas to calculate and adjust the air-fuel ratio.

The function of the oxygen sensor is to reduce exhaust emissions and to know whether the catalytic converter is working perfectly or not. It prevents the engine from running lean or rich by maintaining a perfect air-fuel ratio. It also improves mileage by as much as 40%

High-pressure and temperature exhaust gases when traveling through the exhaust manifold, come in contact with the oxygen sensor, placed before the catalytic converter, which causes voltage production, and that voltage is then sent to the ECU to regulate the air-fuel ratio.

At normal temperatures, the oxygen sensor does not produce a voltage on its own; it produces a voltage when it gets hot at approximately (316 °C) 600 °F. That’s why a heater element is installed inside the oxygen sensor to make its sensing element hot quickly, and the oxygen sensor starts getting hot the moment car starts.

Older single wired-oxygen sensors had no heater and the sensor used to wait for a few minutes for the exhaust gases to make it hot after that it used to produce the voltage. This time lag of when the engine has started, and the sensor starts to produce the voltage causes pollution problems that are connected to the slow start-up process.

On the other hand, the oxygen sensor equipped with the heater is heated through heaters by allowing the current when the engine has started.

Related Post: What Causes An Oxygen Sensor To Fail

Construction Of Oxygen Sensor

Oxygen Sensor Construction
Oxygen Sensor Construction

By shape, the oxygen sensor looks the same as a spark plug. The oxygen sensor has a sensing element at the front of the sensor called zirconium dioxide enclosed within a steel shell.

The sensing element is further connected to the platinum electrode where wires lead to the ECU. The sensing element is placed around a heater core. The heater core has a gap from the inside in which the atmospheric air can travel.

Both the sensing element and heater core have two, two wires. The sensing element has two wires (earth and hot wires), which are connected to the ECU. Similarly, the heater core has two wires (earth and hot wires), and the hot wire goes to the relay in the fuse box.

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O2 Sensor Working Principle

Oxygen Sensor Working Principle
Oxygen Sensor Working Principle

The oxygen sensor working principle is based on ionization, which leads to producing their own voltage. The exhaust gas in the exhaust manifold contains oxygen molecules that hit the sensing element after flowing through the holes in the steel shell. 

Meanwhile, the outside atmospheric air is made to flow through the gaps between the cables at the end of the sensor. The heater core inside the oxygen sensor heats the atmospheric air outside of the exhaust manifold. This heated air enables the ions (electric charge) to produce voltage. 

So, when the exhaust emission flows through the oxygen sensor inside the exhaust pipe, the oxygen concentration in the atmosphere will be high compared to the oxygen molecules present in the exhaust emission.

This difference in concentration of the oxygen molecules in the exhaust gas and the atmospheric air produces ions from higher concentrations to lower concentrations. These oxygen ions’ movement generates voltage difference and causes to build in the voltage in the sensing element.

The ECU then compares it with the pre-stored standard data to decide whether the mixture is rich or lean. And these calculations manipulate the air/fuel mixtures during the subsequent stroke.

Remember, the oxygen sensor does not measure the amount of oxygen present in the exhaust emission but rather the difference between the amount of oxygen in the exhaust gas and the atmospheric air.

Related Post: Oxygen Sensor: 1, 2, 3, 4 Wire O2 Sensor Wiring Diagram

Frequently Asked Questions (FAQs)

How long can you drive with a faulty oxygen sensor?

Assuming you are referring to a vehicle’s oxygen sensor, it is advisable to replace it as soon as possible once it is determined to be faulty. Depending on the severity of the issue, a driver may be able to get by for a couple of days with a faulty oxygen sensor. However, it is not recommended to drive for an extended period of time with a faulty oxygen sensor as it can cause further damage to the engine.

Will an oxygen sensor stop a car from running?

No, an oxygen sensor will not stop a car from running. The oxygen sensor is a part of the car’s emission control system and is responsible for monitoring the oxygen content of the exhaust gas. If the oxygen sensor detects that the oxygen content of the exhaust gas is too low, it will send a signal to the engine control unit (ECU) to adjust the air/fuel mixture. This will help to reduce emissions and improve fuel economy.


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