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What is an Oxygen Sensor?

Sensors In Your Vehicle

Designed to monitor the various systems and parts of the vehicle, sensors are crucial to the operation of today’s technologically advanced vehicles. From monitoring the engine temperature to determining the position of the wheels, sensors collect thousands of data points and sends the information to the Electronic Control Unit (ECU), the brain of your car. The ECU analyzes the data and depending on the situation makes the required changes to ensure optimal performance or vehicle safety.

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What Does An Oxygen Sensor Do?

Key to engine performance and emissions compliance, the oxygen sensor is one of the most important sensors in your vehicle. Also known as an O2 sensor, it is responsible for measuring the amount of unburned oxygen that is in the exhaust. The ECU uses this information to determine the right air-fuel for the engine to complete an efficient combustion process. Through this monitoring, the oxygen sensor can detect if the air-fuel mixture is lean (too much oxygen) or too rich (not enough oxygen).

Operating in real time, the information that the oxygen sensor collects helps the ECU to adjust the fuel injection when necessary. This ability to make changes as needed, means the engine can dynamically adapt to when the driver accelerates, decelerates or is idling.

How Many Oxygen Sensors are on a Vehicle?

Oxygen sensors were first mandated in 1981 and after 1996, vehicles were required to have a second O2 sensor. A vehicle with a single exhaust system has an oxygen sensor before the catalytic converter and one after while vehicles with a double exhaust system will have four O2 sensors. However, many late model vehicles have three or four oxygen sensors. You’ll find an O2 sensor in each exhaust manifold and near the catalytic converter.

How Long Does an Oxygen Sensor Last?

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Despite being exposed to heat and high temperatures, oxygen sensors typically last for 100,000 miles.

What are the signs of a failing oxygen Sensor?

When the vehicle has the right air-fuel ratio, it reduces emissions, maximizes gas mileage and ensures optimal engine performance. A failing or malfunctioning O2 sensor can lead to the air-fuel mixture being imbalanced which can lead to increased emissions, diminished gas mileage and poor engine performance. Be on the lookout for the symptoms of a bad oxygen sensor:

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Decreased gas mileage

A failing O2 sensor doesn’t have the ability to properly regulate the air-fuel mixture which can result in increased gas consumption.

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Power Loss

A loss of engine power while accelerating or sluggish engine performance can signal a faulty oxygen sensor.

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Check Engine Light

A failing O2 sensor can cause the check engine light to illuminate.

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Poor Engine Performance

Rough idling or engine misfires could be the fault of a bad oxygen sensor that has lost the ability to help control combustion intervals and engine timing.

If you notice any of these symptoms, have your auto technician examine the vehicle to make a diagnosis.

Can You Drive with a Bad O2 Sensor?

Driving with a failing oxygen sensor can cause your vehicle to use more gas, leading to more trips to the gas station. In addition, you may experience poor engine performance with a loss of power, rough idling and engine misfires. Also, if you live in a state that does emissions inspections, a bad O2 sensor will result in your vehicle failing the test.

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Learn more about quality sensors, find your car part, or find where to buy your auto part today.


The content in this article is for informational purposes only. You should consult with a certified technician or mechanic if you have questions relating to any of the topics covered herein. Tenneco will not be liable for any loss or damage caused by your reliance on any content.

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