You can expect to spend anywhere from $40.00 to $80.00 dollars on average for a single oxygen sensor. Depending on your vehicle model, you might need to replace more than one, if you are changing components as part of a major tune-up. However, the savings will offset the expense by a great margin. These sensors monitor oxygen content going through the exhaust system and help your car's computer to constantly adjust the air-fuel mixture to the immediate driving conditions, which has an impact on engine performance.
Park your car in a safe, level place and open the bonnet.
Disconnect the black, negative cable from the battery using a wrench, place the transmission in neutral (manual) or park (automatic) and apply the emergency brakes.
Locate the oxygen sensor. Depending on your vehicle model, the exhaust system might be equipped with one, two or more of these sensors, if your engine has one or more exhaust pipes. Follow the exhaust pipe(s) connected to the exhaust manifold and right before the pipe connects to the catalytic converter, you should see a small cylinder, the size of a spark plug, attached to an electrical connector. That's your front oxygen sensor. The other sensor is located close to the rear of the catalytic converter.
Raise the vehicle using a jack and support it safely on jack stands if you need to crawl underneath the car to locate and remove the oxygen sensors.
Unplug the sensor electrical connector, being careful not to break the plastic locking tabs.
Remove the component using a sensor socket and ratchet.
Apply a thin coat of anti-seize compound to the threads of the new oxygen sensor to keep exhaust heat from seizing the unit in place and to prevent thread damage.
Thread the new unit in place by hand first, then use the sensor socket and ratchet to tighten it. Make sure not to over tighten to avoid component damage.
Plug in the sensor electrical connector, lower the vehicle and connect the black, negative battery cable.
If necessary, consult your vehicle's service manual to locate and identify components. You can buy a manual at most auto parts stores or consult one for free at your local public library.
The exhaust system in your car may reach operating temperatures of 1500F. Make sure system components are cool enough to the touch before beginning work around them. Anytime you need to raise your vehicle to reach for components located underside, make sure to support the car on jack stands. Car jacks are not intended for continuous periods of use by themselves. The jack's hydraulic system may fail and collapse under the car's weight.