All You Need to Know about Oxygen Sensors

An oxygen sensor in a Chevy Silverado engine bay

Your vehicle's oxygen sensors are critical to a well-running engine, yet they can be overlooked during regular maintenance. Many owners are unaware of an issue with the oxygen sensors until the check engine light illuminates or fails a vehicle emissions test.

We will discuss the function of an oxygen sensor and the signs and symptoms of a failing sensor so you can more easily rule out other issues and determine when to replace the oxygen sensor.

What is an O2 Sensor?

An O2 sensor, also known as an oxygen sensor (sometimes called an air/fuel ratio sensor), helps your vehicle maintain exhaust and emission levels within the vehicle's acceptable limits. Your vehicle requires fuel, air, and spark for combustion for the engine to run. An O2 sensor monitors your vehicle's exhaust to determine how much oxygen it is, reporting to the engine's computer, known as the Engine Control Module, in order to establish the ideal air/fuel mixture for maximum engine performance. When there's too much air and not enough fuel, the sensor informs the ECU, reducing timing or adding additional fuel to reach ideal combustion.

In addition to causing poor engine performance and decreased fuel mileage, a bad O2 sensor will significantly impact the environment by releasing increased levels of pollutants into the air. Left unchecked, driving with a bad O2 sensor can cause severe engine and catalytic converter issues, potentially costing thousands of dollars to fix.

Multiple O2 sensors will be used in newer cars to supply the engine computer with two readings and additional data. Before and after the catalytic converter in the exhaust pipe, there are upstream and downstream O2 sensors, commonly known as sensor 1 and sensor 2, respectively. The upstream sensor monitors burn efficiency for the ECU to calculate the ideal air-fuel ratio to provide the most power and ensure the engine runs efficiently. The ECU then compares the downstream readings with the upstream readings. If the burn levels are too similar, a diagnostic trouble code will indicate the catalytic converter is not functioning correctly.

Diagnosing a Bad O2 Sensor

Because O2 sensors are a critical exhaust component that affects engine performance, owners should replace them approximately every 60,000 to 90,000 miles. Knowing the signs and symptoms of a failing O2 sensor will help you determine when to replace it.

A check engine light or an on-board diagnostic trouble code will illuminate with a misfire caused by the failure of an O2 sensor. If these lights come on, it is best to run a diagnostic test to determine what the ECU believes to be the issue.

If your car starts to run rough, you notice a lack of power on acceleration, engine stalling, or extremely poor gas mileage; it might be time to replace your O2 sensor.

If you smell exhaust fumes inside your car when you first start the engine, this could also indicate a problem with your O2 sensor. Additionally, a rotten egg smell results from burning sulfur resulting from a failed sensor causing a poor air/fuel mixture, which can damage the catalytic converter.

One of the most common reasons for failing an emissions test is faulty O2 sensors. To save time and money, have the sensors examined by a mechanic before taking an emissions test.

O2 Sensor Replacement

If your vehicle has been having these issues, do not hesitate to replace the O2 sensor. It will extend the life of your vehicle and contribute to a cleaner environment. If you have some basic knowledge of cars and engines and the proper tools, you can replace the sensor yourself.

O2 sensor replacement is a fairly routine maintenance item for an experienced mechanic or service center. It is a good idea to have the O2 sensors examined when the automobile isn't running properly and when completing routine maintenance such as oil changes.

Swap Your O2 Sensors Out at Valley Chevy

Your vehicle's O2 sensors are often neglected but vital to your vehicle's health and proper operation. Any ignored issue can compound into costly problems in both your exhaust and the engine itself.

Valley Chevy group of Chevrolet dealerships in the Phoenix metro area has a dedicated staff committed to providing you the excellent customer service you deserve. If your vehicle is exhibiting any of the symptoms mentioned earlier, or you would like a multi-point vehicle inspection completed during your next scheduled maintenance appointment, stop by any of our Valley of the Sun dealerships today!

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