Where Are Oxygen Sensors Located?

Q: Where Are the Oxygen Sensors Typically Located?

A: Oxygen sensors are located in the vehicle’s exhaust system. Most vehicles are equipped with two oxygen sensors. An upstream oxygen sensor is mounted before the catalytic converter. Meanwhile, a downstream sensor is mounted after the cat-con.

Oxygens sensors measure the amount of oxygen in the exhaust. Your vehicle’s powertrain control module (PCM) uses the data from these sensors to calculate the proper amount of fuel needed by the engine. The input from the downstream sensor is also used to monitor the health of your catalytic converter.

Tips on How to Access the Oxygen Sensors

Pro Tips are nuggets of information direct from ASE-certified automobile technicians working with CarParts.com, which may include unique, personal insights based on their years of experience working in the automotive industry. These can help you make more informed decisions about your car.

Pro Tip: Do the procedures below with a cold engine so you won’t get burned. There’s no reason to warm the engine or the exhaust.

In most modern vehicles, you can find two sensors near the motor and two sensors near your catalytic converter. An oxygen sensor resembles a spark plug. It looks like a small metal device with wires coming out of it.

If you’re accessing the oxygen sensors because of a fault code, you’d have to be sure which particular sensor needs to be inspected and/or replaced.

You’ll usually need a special tool (there are several varieties of these), but even with the tool it can be difficult to remove the sensor sometimes because of where it’s located. Sometimes it’s even difficult to disconnect and reconnect the wires for the same reason.

If you’re removing and reinstalling the same sensor, use some anti-seize compound on the threads. New sensors come with it. If you don’t, you may not be able to remove the sensor again without destroying the threads in the converter or exhaust.