Mechanics

Oxygen Sensor 02 Replacement

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How to Replace an Oxygen Sensor

Your car's oxygen sensor is designed to monitor the amount of oxygen is in the exhaust system at any given second. This is done by using an active chemical that when heated can act as a low voltage generator. Follow this link to see how an oxygen sensor works. There are many conditions that can cause an oxygen sensor to miss-behave even though there is nothing wrong with the sensor, to be sure the sensor is the problem by visiting how to test an oxygen sensor. Older cars will have just one sensor in the exhaust system while newer cars will have as many as four sensors. The reason behind the multi-sensor cars is control and monitoring capabilities. A multi-sensor system will be able to monitor the exhaust gasses before and after the catalytic converter.

Most sensors are designed with a heater element to aid the sensors functionality when cold. Failure of this element is common and will warrant sensor replacement. When a sensor or the heating element inside the sensor fails it will trigger a check engine or service engine soon light in most cases. If this occurs connect a scanner tool to your vehicle to access the diagnostic trouble code to help pin point the failed sensor. Once you have determined which oxygen sensor has failed, or you would like to simply replace the sensor to test for a problem you will need to follow these instructions to replace it. When a O2 sensor fails it can cause the engine to run lean or rich depending on the failure.

Before we start, park your car on level ground and allow to cool. Block the tires to prevent the vehicle from moving. Lift the car with a floor jack in the manufacturers recommend position. Use jack stands to secure the car. The sensor is located in the exhaust system so be careful of hot components. Make sure to wear protective clothing, gloves and eyewear.


Tools and Supplies Needed to Complete this Job

1. Screw Driver Set

2. Wrench set with large sizes

3. Shop Towels

4. Anti-Rust penetrating oil such as WD40

5. Replacement Oxygen Sensor

6. Wire Brush


Instructions

Step 1 - Locate the hood release activation lever and operate it. This will "pop" the hood open and allow you access to the engine.

Step 2 - Once the hood is open and secure locate the failed sensor. Most sensors are located in the head pipe or downpipe and behind the catalytic converter.

Step 3 - Spray a anti-rust lubricate over the sensor near the mounting threads and seat of the oxygen sensor and allow to penetrate.

Step 4 - Locate and release the electrical connector. (Note: Some sensor wire leads can be quite long so you may need to follow the wiring harness to locate the connector)

Step 5 - Now that the electrical connector is disconnected use a wrench to loosen the sensor by turning the sensor counter clockwise. Continue to loosen the sensor until free.

Step 6 - Use a wire brush to help clean the threaded port to ensure a proper seal of the new sensor.

Step 7 - Match the old sensor to the new sensor to make sure you have the correct part. (Note: some replacement sensors have a universal electrical connector that will need to be configured to the wiring of the old sensor).

Step 8 - Install the new sensor and firmly tighten the sensor's sealing ring against the threaded port in the exhaust system.

Step 9 - Re-connect the electrical connector and secure the wiring harness into the plastic holders. (If any)

Step 10 - If the car has diagnostic trouble codes, they will need to be cleared in all cars built after 1996. If the codes are not cleared the check engine light will remain illuminated until the system cycles the code out and clears itself.


Best Practices

  • Use an anti rust treatment to help in the removal of the sensor
  • A specially designed socket or wrench can be used to aid in the removal of hard to access sensors
     
If further assistance is needed, our certified car repair technicians are ready to answer your car questions. Also, gain manufacturer specific instructions and information by clicking - Auto Repair Manual


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AUTHOR


Written by
Co-Founder and CEO of 2CarPros.com
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-08-16)