How to Change an Oxygen Sensor

The first indication that there is a problem with your vehicle's oxygen sensor is when the "Check Engine" light comes on. A quick check with a handheld diagnostic scanner/reader will confirm that you need to change the oxygen sensor on your vehicle. Depending on the make and model of your vehicle, there will be between two and four O2 sensors located on your exhaust system. There is at least one sensor in front of the catalytic converter, plus one in each of the car’s exhaust manifold.[1] The diagnostic scanner/reader should tell you which bank of sensors has gone bad.


  1. Image titled Change an Oxygen Sensor Step 1
    Locate the oxygen sensor on your vehicle by looking for a part that looks like a spark plug that sticks out from the exhaust pipe. It will have an electrical connection attached to it.
  2. Image titled Change an Oxygen Sensor Step 2
    Disconnect the electrical connection on the oxygen sensor. Use a flat tip screwdriver to push in the tabs and pull the connection apart.
  3. Image titled Change an Oxygen Sensor Step 3
    Unscrew the oxygen sensor off the exhaust pipe using either an open-end wrench or a special socket made to remove it. The majority of oxygen sensors will take an SAE 78 inch (2.2 cm) wrench.
  4. Image titled Change an Oxygen Sensor Step 4
    Compare your new oxygen sensor to the old one. If the new one did not come with an electrical connection, but just with the wires stubbed out, you need to do a little work.
    • Cut off the old connector from the bad oxygen sensor, strip the wires and solder the wires to the new oxygen sensor. You can also use butt connectors.
    • Use heat sensitive shrink tape to seal the connections.
    • Follow manufacturer's instructions to know which wires to tie together.
  5. Image titled Change an Oxygen Sensor Step 5
    Reverse the steps used in removing the oxygen sensor and install the new part. Add a small amount of anti-seize to the threads of the new sensor. Screw it in place clockwise and snug it down with the socket or open-end wrench. Do not over tighten the sensor as you might strip the threads.
  6. Image titled Change an Oxygen Sensor Step 6
    Plug the electrical connections back in.
  7. Image titled Change an Oxygen Sensor Step 7
    Turn on the ignition key, but do not start your vehicle. Use the diagnostic scanner/reader to clear the code from the vehicle's computer.
  8. Image titled Change an Oxygen Sensor Step 8
    Start the car. You should notice an immediate improvement.


  • Penetrating oil sprayed on the old oxygen sensor threads will help loosen a stubborn oxygen sensor.
  • A defective catalytic converter can cause an oxygen sensor code to the rear sensor.
  • You can ask the parts house where you bought the oxygen sensor to use their reader to clear the codes when you return the tool you borrowed.
  • The parts house where you bought the oxygen sensor will use their diagnostic scanner/reader to tell you which oxygen sensor to change and loan you the special socket wrench.


  • Always allow the engine and exhaust system to cool down before you begin work to prevent accidentally burning yourself.
  • You will need to jack up the vehicle to change the oxygen sensors behind the catalytic converter. Be sure to practice good safety by using jack stands and eye protection while you're under the vehicle.

Things You'll Need

  • Oxygen sensor
  • Soldering iron or butt connectors
  • Heat shrink electrical tape
  • Heat gun or butane lighter to shrink the tape
  • Open end wrench
  • Oxygen sensor removal socket and wrench
  • Penetration oil
  • Car jack
  • Jack stand
  • Safety eyeglasses
  • Auto diagnostic scanner/reader
  • Electrical wire stripper and crimping tool
  • Flat bladed screwdriver

Article Info

Categories: Car Maintenance and Repair