Auto Repair Blog

Published 11:00 AM, Tue June 9, 2015

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What does an oxygen 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 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 engine; and a downstream sensor
  • 4 and 6 cylinder 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 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.  


  • Billy

    thanks for such an informative article!

  • Miguel

    Does a bad oxygen sensor make your car shuts off

    • Richard Karkkainen

      No. It will trigger the check engine light. It is best to have it replaced for the health of your car’s engine and your own.

    • Germz


  • Sarah Handstitch

    How costly to replace O2 sensor and labor cost?

    • Linda Garcia

      I would like to know the cost to repair O 2 sensor

      • Germz

        U can not repair them. You must replace them. The price is erratic as I have seen them for 14$ and I have seen them for 180$

        • Lori

          Hi Germz, I have a 2010 BMW and the code is showing up as the oxygen sensor, prior to that the code was misfire #6. #6 coil was replaced and now it shows the oxygen sensor. The mechanic doesn’t believe it is the oxygen sensor since my car has 69k miles on it and advised me to hold off for a while and upgrade to the premium gasoline rather than repairing the sensor right away. He said the service engine light may go away on its own in a couple of weeks. What do you advise?

          • Germz

            This is true! the code may go away on its own. Check with BMW to see if you can disconnect the battery to reset the computer. (CHECK WITH THE DEALER FIRST!!!!!, I have seen BMWs have to go back to the dealer to have the computer flashed because of loss of power) Normal cars you can disconnect the battery and reset the computer. This sets the computer as if it came off the line. It will run funny for a little while. like an hour as it makes little adjustments. If the code pops back on… you more then likely need a new o2 Sensor. Or, do as your mech says and drive it for a while. But, not too long because if you ignore the o2 sensor malfunction, your catalytic converter will burn out. So, I would not advise going for more then a few weeks. Now for my opinion: Because you had a misfire in the cylinder, the O2 sensor could have burned out simply because that cylinder was not burning all of the fuel that it was issued and when the cylinder pushes the exhaust out, it was pushing gas vapors out and they went right to the o2 sensor. This burns them out. The O2 sensor checks to see if the car is burning fuel correctly and or that the mixture is correct. If it is burned out, the car will sacrifice performance and longevity in order to not pollute.This means the dominoes will fall if you do not take care of this. If I had to guess, I would say you have a bad o2 sensor, they go bad all the time. For your vehicle… I don’t know. I have seen o2 sensors for 25$ and I have seen them for 300$. if it stays on for 2 weeks, replace it. If the dealer DOES tell you that you can disconnect the battery, run the car for 100 miles and see if the light comes back on and gives you the same code. If so, replace it.

    • Linda Garcia

      How costly is it to repair o2 sensors on 2014 Honda accord

    • Germz

      THis depends on car

  • J Eckle

    What is the danger of not having the O2 sensor fixed?

    • Germz

      damage to catalytic converter $$$. waste of gas. damage to engine. but this all depends on the current mixture/ratio of O2 and gas

  • Linda Garcia

    How much does it cost to repair O2 sensor for 2014 Honda Acord

    • Germz

      Linda if you find a price on that O2 sensor, get me a link to prove the price and i will beat it by over 50%!

    • Germz

      Linda ill beat the price on that o2 FB “Jermz Optional Davieau”

  • Heaven Lewis

    Could this be why my 93 ls400 lexus has a lack of power? The catylact converter was clogged (but has been cleaned) but do you think it may have caused the 02sensor to overheat causing damage to it? Colud that be the answer to the lack of power?

  • Jennider

    What can cause ur car to stall off if ur just sitting in line, I paid 500.$ for wheel Barnes, when now I think its the o2, cause My
    engine light stays on ? Could it b the O2 ?????

  • Jennider

    My car stalls when I’m just sitting in take out line, I just spent 500.$ on the wheel Barnes, but now I think it might b my O2, and the check engine light stays on ???? What do u think?

    • Jacob Cornell

      take it to autozone or somewhere else and have them read the codes. If your check engine light is on they can read the codes and pull up what is exactly wrong according to your cars computer.

  • Ridi

    My car looses power. Doesn’t have acceleration. The mechanic told me it is the oxigen sensor. That whas on the computer. The question is. Do i have to find the other one by the numbers on the sensor? And how to know if it is the sensor near engine that doesn’t work or the other one that is positioned at the exhaust? Thanks

    • Jacob Cornell

      Take it to autozone or somewhere else and have them read the codes. If
      your check engine light is on they can read the codes and pull up what
      is exactly wrong according to your cars computer. They may be able to tell you which one whether it is Sensor 1 or 2.

  • hagfan57

    I had my 97 Land Cruiser (6 cyl) Cat Converter cut off a while back. Went to a straight pipe. Still has two 02 sensors on it though. MUCH better performance. But MPG has remained the same. Trying to improve that. Can I eliminate my 02’s since my CC is gone? Might that improve my mileage? Thanks!