Where Is the O2 Sensor Located?

Oxygen sensors O2 sensors will always be located in the exhaust system. Their function is to sense how much oxygen remains in the exhaust that is flowing out of the engine, and report that information to the vehicle’s engine control computer.

This information is then used to help with accurate fuel delivery to the engine under various driving conditions. Your vehicle’s main computer, the powertrain control module, monitors operation of the O2 sensors. If a problem is noted, the Check Engine Light will illuminate and a diagnostic trouble code will be stored in the PCM’s memory to assist a technician with the diagnostic process.

A couple helpful tips to assist in locating O2 sensors:

  • Vehicles built after 1996 will have at least two O2 sensors
  • 4 cylinder engines will have two oxygen sensors
  • V-6 and V-8 engines will usually have 3 or 4 oxygen sensors
  • The sensors will have 1-4 wires on them
  • The front sensor(s) will be located under the hood, on the exhaust, very close to the engine
  • The rear one(s) will be located under the vehicle, directly after the catalytic convertor

The sensor(s) close to the engine are sometimes called “pre-cat”, being located before the catalytic convertor. This O2 sensor provides information about oxygen content in the exhaust before it is treated by the catalytic convertor. The O2 sensor located after the catalytic convertor is referred to as “post-cat” and provides data about oxygen content after the exhaust has been treated by the catalytic convertor.

When replacing O2 sensors that have been diagnosed as faulty, it is strongly recommended to obtain original equipment brand sensors. They are designed and calibrated to work with your vehicle’s computer. If you have a V6 or V8 engine, replace sensors on both sides at the same time for best results.


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Recent Oxygen Sensor Replacement reviews

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Jose

12 years of experience
49 reviews
Jose
12 years of experience
Chevrolet Silverado 1500 V8-4.8L - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - Moreno Valley, California
very knowledgeable and honest , professional and clean explain everything to me and answer all m,y question
Scion tC - Oxygen Sensor Replacement (Rear/Lower/Downstream) - Sun City, California
Arrived in a timely manner, was very professional and knowledgeable about any questions. Would definitely recommend to anybody (family, friends, etc) looking for a mechanic!

Joel

11 years of experience
146 reviews
Joel
11 years of experience
Honda CR-V L4-2.4L - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - Frisco, Texas
I have not seen a more sincere and hard working person than Joel. This, on top of his great skills and know-how of working with an automobile and a very friendly, likeable personality. Unfortunately, it took multiple attempts to fix the Check Engine light on my vehicle. The car needed O2 sensor replacement but due to a couple of reasons the problem was not getting fixed. So Joel would come, run the tests, fix the problem, do the test drive, and leave thinking the problem has been resolved only to find out from me later that the Check Engine light is back on. However, Joel followed up patiently with me over the course of couple of months to ensure that the problem was fully resolved, even if it took him a couple of visits. Well, he has my business from now on and full trust for my cars! Thank you, Joel!
Ford Expedition - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - Denton, Texas
Joel showed up right on time. Replaced O2 sensors on my Ford Expedition. Ran a diagnostic as well & verified fuel trims etc. Was in and out within an hour. Ensured my driveway was clean when he left and did not leave any mess. I was very pleased with his professionalism. Definitely recommend Joel for auto repair.

James

30 years of experience
873 reviews
James
30 years of experience
Toyota Camry V6-3.5L - Oxygen Sensor Replacement (Rear/Lower/Downstream) - Orlando, Florida
Mr. James dis an awesome job on my 2007 toyota camry. He was punctual and professional. He fixed the problem very quick.
Toyota Avalon - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - Apopka, Florida
VERY WELL EDCUATED AND VERY SMOOOTH- I KNOW WHO TO CALL WHEN I NEED A SPARE HAND! LOL! AWESOME PERSON AND THANK YOU FOR SERVICES!

Shane

17 years of experience
217 reviews
Shane
17 years of experience
Ford F-150 V8-5.4L - Oxygen Sensor Replacement (Front/Upper/Upstream) - Cedar Park, Texas
Shane is great. I will be calling on him soon on other vehicles I own. Thank you Shane for a great job.

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