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What Does An Oxygen Sensor Do?

Published Fri June 9, 2017

what does an o2 sensor do

 

As a vehicle owner, the last thing you want to see is the bright orange “Check Engine” light burning. This alert is almost always the result of a tripped oxygen, aka O2, sensor. Another warning sign could be the message on your car’s computer that there is a heater circuit malfunction. When you see the Check Engine Light (CEL) or heater circuit malfunction message it could mean that your O2 sensor has simply gone bad. Of course, it could also mean that your vehicle is not running properly resulting in an excessive amount of emissions. Whatever the case, taking your vehicle in for a tune-up is the best bet to ensure that your vehicle’s O2 sensor is in top performance.

 

What is an Oxygen Sensor?

 

The oxygen sensor, also known as a lambda sensor, was developed in the late 1960s by Dr. Gunter Bauman for the Robert Bosch GmbH company. This sensor is an electronic device used to measure the proportional amount of oxygen in a liquid or gas. The original oxygen sensor was made using ceramic coated zirconia and platinum. In order to make the O2 sensor more capable of mass production, planar oxygen sensors were developed. This modernized O2 sensor was developed by NTK in 1990 for use in the Honda Civic and Accord. Made using layers of High-Temperature Cofired Ceramic (HTCC) green tapes, the current style of the sensor is made more efficient than the original style sensors.

 

What Does an Oxygen Sensor Do in a Car?

 

All cars that were manufactured post-1980 feature an oxygen sensor. It is located within the emissions control system. When functioning, the O2 sensor sends data to the management computer located within the engine. In your car, a functioning O2 sensor ensures that your engine is running at top performance. Additionally, this sensor keeps your emissions in check and alerts you to when emissions are too excessive. For states that have vehicle inspection programs to regulate emissions, the use of the CEL and O2 light will alert officials to any excessive emissions. As a result, if one or more of your oxygen sensors is faulty during an emissions inspection for your car, you will most likely not pass the inspection.

 

How Many Oxygen Sensors Are in a Car?

 

Cars with O2 sensors have a minimum of one sensor in front of the catalytic converter, as well as one in each of the car’s exhaust manifold. The actual number of oxygen sensors for a car depends on the year, make, model and engine. However, most of the later model vehicles have four oxygen sensors. Note the following specific vehicles that have four oxygen sensors:

 

  • 2013 Honda Civic 1.8L 4 cylinder
  • 2010 Chevrolet Tahoe 6.0 L 8 cylinder
  • 2004 Jeep Wrangler 4.0L 6 cylinder
  • 2000 Toyota Land Cruiser 4.7L 8 cylinder

The number of sensors varies according to engine type:

 

  • Traditional V6 and V8 have three oxygen sensors including a left bank and right bank sensor upstream and a downstream O2 sensor
  • 4 cylinder transverse has an upstream and a downstream O2 sensor
  • V6 and V8 transverse have four oxygen sensors including a left or front bank upstream; right or rear bank upstream; rear of the engine; and a downstream sensor
  • 4 and 6 cylinders in-line have three oxygen sensors including a front and rear bank upstream and a downstream sensor

What Do Oxygen Sensors Do?

 

When a gasoline-powered engine burns gasoline there is oxygen present. Oxygen in an engine is the result of a number of factors including the air temperature, altitude, engine temperature, load on the engine, and barometric pressure. The ideal ratio for oxygen and gasoline is 14.7:1, which slightly varies depending on different types of gas. In the instance that there is less oxygen present fuel will remain after combustion, which is referred to as a rich mixture. On the other hand, if there is more oxygen present it is referred to as a lean mixture. Both the rich and lean mixtures are bad for your car, as well as for the environment. A rich mixture results in a fuel that is not burned that creates pollution. A lean mixture generates nitrogen-oxide pollutants, which can lead to decreased vehicle performance and engine damage. Oxygen sensors are positioned near points in the exhaust system so to determine if there are rich or lean mixtures in your car.

Typically, an O2 sensor creates a voltage due to a chemical reaction resulting from an off-balanced gasoline to oxygen ratio. Most car engines can determine how much fuel to expend into the engine based on the voltage of the O2 sensor. If your oxygen sensor fails to function properly, your engine management computer cannot determine the air to fuel ratio. Therefore, the engine is forced to guess how much gasoline to use, resulting in a polluted engine and a poorly functioning vehicle.

 

How to Test an Oxygen Sensor

 

To test your oxygen sensor, you can either leave it attached to your vehicle or take it off for testing. Testing requires two tools: a high-impedance digital voltmeter and a backprobe. A mechanic at a Meineke repair shop has these necessary and specialized tools for checking O2 sensors. The first step to checking an O2 sensor is to locate the surrounding wires to make sure they are intact and without visible signs of wear and tear. Next, the vehicle must be started and allowed to run until the engine reaches 600 degrees F so to ensure an accurate reading of the sensor. Using the back probe and voltmeter, the oxygen sensor is measured at a set number of points and under particular conditions to determine any faulty measurements. As the testing of an oxygen sensor requires specialized training and tools, it is best to allow a mechanic to handle this voltage-based testing.

To schedule an oxygen sensor testing, bring your car into your local Meineke Car Care Center where you can let the car care professionals handle the precise work of oxygen sensor testing.  

 

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