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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James

23 years of experience
25 reviews
James
23 years of experience
Lexus ES350 - Oxygen Sensor Replacement (Front/Upper/Upstream) - Marietta, Georgia
James was great!! He answered all my questions, was patient and professional. I don’t want to have to use a mechanic any time soon but if I have to I would request James.
Chevrolet Malibu - Oxygen Sensor Replacement (Front/Upper/Upstream) - Austell, Georgia
Very nice, very knowledgeable, and got the job a lot quicker than I expected. He even recommended what should be done next. Extremely helpful. Would recommend.

Chuy

14 years of experience
277 reviews
Chuy
14 years of experience
Toyota Corolla - Oxygen Sensor Replacement (Front/Upper/Upstream) - Chicago, Illinois
Outstanding performance done by Chuy. Not only he did what I asked to do, but also he took care of small details that I would have not caught otherwise! I’d ask Chuy for any other services in the future.
Subaru Outback - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - Villa Park, Illinois
Church had to work extra hard to make sure that the repairs were properly done. The work was completed to my satisfaction. Thank you.

Kenneth

20 years of experience
653 reviews
Kenneth
20 years of experience
Hyundai Santa Fe - Oxygen Sensor Replacement (Rear/Lower/Downstream) - Los Angeles, California
Kenneth came early and did the work in record time. He also made recommendations for additional things ne noticed needed to be done.
Chevrolet Suburban 2500 - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - Pico Rivera, California
Great communication with updates on vehicle status and recommended services. Would recommend and book again for maintenance needs.

Gustavo

17 years of experience
269 reviews
Gustavo
17 years of experience
Chevrolet Cruze - Oxygen Sensor Replacement (Front/Upper/Upstream, Rear/Lower/Downstream) - San Antonio, Texas
There is nothing negative to say about the services rendered. Best experience ever getting a vehicle fixed. I will be a repeat customer.

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