Oxygen Sensor Buyer's Guide
- Oxygen sensors work by monitoring the amount of oxygen in the exhaust pipe. An oxygen sensor sends a signal to the Engine Control Unit (ECU) to adjust the amount of fuel injected in the combustion chambers.
- The three most common types of oxygen sensors are the Zirconia 02 sensor, Titania 02 sensor, and Wide Band 02 sensor.
- Faulty oxygen sensor signs include rotten egg smell from exhaust pipes, irregular engine idling, and poor gas mileage.
- It is important to have a faulty oxygen sensor replaced because not only does it cause harm to the environment, but it’s also vital to your vehicle’s overall performance.
Car pollutants cause long-term damage to the environment. However, car owners can reduce the amount of harmful substances emitted by their car’s exhaust system with the help of an oxygen sensor. Apart from helping the environment, oxygen sensors also play a role in keeping your car engine’s health at its best.
What is an oxygen sensor and how does it work?
Oxygen sensors work by monitoring the amount of oxygen in the exhaust pipe. Too much or too little oxygen is not good for the engine’s health. The oxygen sensor helps create a balance by sending a signal to the Engine Control Unit (ECU) to adjust the amount of fuel injected into the combustion chambers.
Oxygen sensors can either be installed in the front or rear of the car. A front oxygen sensor is installed at the front exhaust pipe near the catalytic converter or at the exhaust manifold. It is responsible for keeping the air-fuel ratio at an ideal level. In some cars, an air-fuel ratio sensor is sometimes used instead of a front oxygen sensor.
A rear oxygen sensor is mounted right after the catalytic converter. It is usually mounted in the exhaust itself. The rear oxygen sensor is usually used to monitor the performance of the catalytic converters.
Volvo was the first to use oxygen sensors in the1970s. The first oxygen sensors were made from Zirconia, with only one or two wires on it. Older vehicles were only equipped with one oxygen sensor. Every automobile manufactured after the 1980s is equipped with an oxygen sensor.
Over the years, the demand for oxygen sensors has changed. Today’s vehicles can have up to eight oxygen sensors, depending on capacity. Cars with 4-cylinder engines usually have two oxygen sensors installed, while other vehicles with V6 and V8 must have at least four oxygen sensors installed.
What are the types of oxygen sensors?
There plenty of oxygen sensors available today. These can be classified into three types: Zirconia O2 sensors, Titania O2 sensors, and Wide Band O2 sensors.
Zirconia Oxygen Sensors
Zirconia oxygen sensors are the most common type of O2 sensors. This type of oxygen sensor can further be classified into unheated and heated zirconia oxygen sensors.
Unheated oxygen sensors rely on heat to send signals to the ECU. One drawback is that it takes a lot of time for the exhaust to heat up and the signal may not be sent the signal at the right time. This may confuse the ECU, causing it to go back to its default setting and releasing the wrong amount of fuel to the combustion chambers.
Heated oxygen sensors are more advanced because it has a heater circuit installed. This automatically heats up the sensor when starting the car, making it more efficient than unheated oxygen sensors. A heated oxygen sensor also decreases the possibility of error by sending timely, accurate signals to the ECU.
Titania Oxygen Sensors
What makes this type unique is that it is made of a ceramic material rather than the usual zirconia. It also uses a different process in sending signals to the ECU. Titania oxygen sensors are usually found in limited edition vehicles only.
Wide-Band Oxygen Sensors
This is a new type of oxygen sensor which is not yet widely used. This type of sensor creates a higher level of voltage than a zirconia oxygen sensor, making it more efficient in balancing the air-fuel ratio in the engine’s exhaust pipes.
When is the right time to replace an oxygen sensor?
It is important to have a faulty oxygen sensor replaced because it can cause serious performance problems.
Have your car checked by a mechanic as soon as the “check engine light” illuminates. If you notice an unusual smell, similar to rotten eggs, coming from your engine’s exhaust, it's likely that your oxygen sensor is bad. Other signs to look out for are irregular engine idling and poor gas mileage.
What to consider when buying an oxygen sensor?
An OEM replacement oxygen sensor is usually priced at $20 to $100. Take note that O2 sensor prices will really depend on the model and make of your car. Some are priced more than the estimate. Aftermarket oxygen sensors are also available.
Oxygen sensors are usually sold individually or in sets of two and four. If you want to replace an oxygen sensor yourself, check your manual to ensure you have the correct specs for a replacement.
Which oxygen sensor should you buy?
Installing the wrong type of oxygen sensor can cause problems in the vehicle. With today's automobiles equipped with at least two, or even three or four oxygen sensors, it can be a challenge to identify which one is not working correctly if you don't have enough DIY auto repair experience. The information below can help you learn more about oxygen sensors, so you can get the correct replacement for your vehicle.
Oxygen sensors are always numbered this way:
- Bank 1 Sensor 1
- Bank 2 Sensor 1
- Bank 1 Sensor 2
- Bank 2 Sensor 2
Other manufacturers code their oxygen sensors this way, which is why it can sometimes be very confusing. However, they all mean the same:
- Sensor 1/1 or O2s 1/1
- Sensor 2/1 or O2s 2/1
- Sensor 1/2 or O2s 1/2
- Sensor 2/2 or O2s 2/2
Now here's a detailed list to know which is which:
- Bank 1 is located at the side of the engine where cylinder #1 is found as well.
- Bank 2 is on the opposite side of Bank 1.
- On a 4-cylinder engine, there is only one bank that's called Bank 1.
- Sensor 1 is the upstream sensor located before the catalytic converter.
- Sensor 2 is the downstream sensor located after the catalytic converter.
- Sensor 3 is the only downstream sensor in situations where there are two sensors before the catalytic converter and only one after it. On other cars, this is read as Bank 1 Sensor 3.
CarParts.com has a high-quality oxygen sensor for every application (upstream, downstream, before / after catalytic converter). Our O2 sensors are sourced from the most reputable manufacturers in the industry, so you can rest assured that you're getting a high-quality replacement. Enter your vehicle's year, make, model, and engine into our vehicle selector to narrow down our selection to your application.