Important Things About Oxygen Sensor You Ought To Know

What Is Oxygen Sensor?

The oxygen sensor is situated at the tip of the exhaust pipe and is used to detect the oxygen levels in the exhaust as it gets released from the engine. This check is important to understand whether the engine is running too rich or lean. In rich condition the oxygen content is found to be low and in lean condition it is the opposite. This information helps the ECU to adjust the fuel entering from the fuel delivery system to the engine for proper combustion and correct fuel to air ratios. If not corrected, it may lead to increased fuel consumption and increased emissions from the exhaust. It may also damage the catalytic converter and the engine components as well.

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Types of Oxygen Sensors

There are two types of oxygen sensors used in vehicles today: The Binary and the Universal Exhaust Gas Oxygen (UEGO) sensors.


  1. Binary Exhaust Gas Oxygen Sensor - The binary sensor works at an operating temperature of 350 degree Celsius and generates electric voltage with respect to the oxygen levels in the exhaust system. This level of oxygen in then compared with the oxygen level in the ambient air to identify rich or lean engine condition.
  2. Universal Exhaust Gas Oxygen Sensor - This sensor is more accurate and faster in realizing the lean or rich mixture for optimal fuel to air ratio compositions. Most of the time it is accompanied by a heated exhaust oxygen sensor to help the UEGO sensor get heat up faster and aid in emission control at a much faster rate. Thus, the heated sensors no longer have to be installed close to the engine for operation.

Important Feature of Oxygen Sensor

The oxygen sensor has two prime objectives. First is to measure the oxygen levels in the exhaust to aid in proper fuel to air ratio for appropriate combustion process to take place. Second is to help in reduction of harmful exhaust emission by controlling the process in the first step.

How Does Oxygen Sensor Works?

Like any combustion process, when the mixture or fuel and oxygen gets burnt in the engine chambers, gases get released. These gases constitute of many elements like oxygen, carbon and many more. The gases find their way out of the exhaust pipe. As these gases pass through the exhaust system, it finds a component called oxygen sensor on its way out in the exhaust manifold. This sensor calculates the amount of oxygen left unused in the combustion process and expelled out with other gases.


This information is then sent to the Engine Control Unit for further analysis. The ECU is responsible for proper functioning of the engine and the associated components which may also include many other sensors. The ECU is like the brain of the engine collecting all the data and making the right decisions.


After the ECU has analyzed the oxygen levels it will know if the combustion process is taking place properly or not. Thus, it will know if the engine is running lean (more air, less fuel) or rich (more fuel, less air). It will then instruct the fuel delivery system to act accordingly. Thus, the fuel entry levels will be adjusted for proper combustion to take place. This will also reduce harmful gas emissions from the exhaust system.

Frequent Problems for Oxygen Sensor

The first sign for any problem with the O2 sensor in the Malfunction Indicator Light getting on. Take the help of a diagnostic scan tools to be sure that the oxygen sensor hasmalfunctioned. The diagnostic trouble codes (DTC) may also indicate if the sensor has gone bad.


Other indications include increased fuel consumption, poor engine performance, black smoke from the exhaust and failed emission tests.

Symptoms of a Bad One Oxygen Sensor?

The Powertrain Control Module (PCM) uses the information from the oxygen sensor to determine the correct air to fuel ratio for the engine in real time. The O2 sensor allows the fuel delivery system and the engine timing to work perfectly and to control the exhaust emissions at the same time. If the oxygen sensor goes bad, it may lead to increased harmful emissions as engine running rich or lean condition along with affected fuel economy. It may also cause other components to malfunction.


  1. Check Engine Light On - Check Engine Light is always the first indication of almost any problems with the car. Thus, this indication along with other confirmed symptoms to a bad O2 sensor can be very helpful. It is advisable to seek professional help when you see this light getting illuminated on the vehicle’s dashboard to inspect for the problematic area and diagnose the problem.
  2. Bad Gas Mileage & Rotten Egg Smell - If the O2 sensor has malfunctioned, the air to fuel ratio may get disturbed, affecting the fuel consumption and combustion process. Normally you will see a rise in fuel consumption as an indicator. Excess fuel in the chambers can cause Sulphur deposits leading to rotten egg smell from the engine and increased emissions accompanied by black smoke from the exhaust.
  3. Rough Engine Idle & Misfires - If the O2 sensor had gone bad, the engine timing may go off. This can result in poor engine performance leading to poor idle, stalling, engine misfires, loss of power, noise from the engine and even smoke.

Tools Needed for Oxygen Sensor

If you want to repair your oxygen sensor all by yourself, then let’s face it that you will need some auto body tools. You can always start by building your own tool chest. Searching for some tools needed to repair your oxygen sensor? Don’t Worry! We are here to help you out. Here are some common tools that you will probably end up needing while repairing your oxygen sensor.


  • Open Headed Wrench
  • O2 Sensor Socket Wrench (optional)
  • 22mm Sockets

Top Brand for Oxygen Sensor

If customers trust a brand, then it would make them loyal, and if they are loyal, then they will surely buy more. We are well aware that customers want comfort, cheerfulness as well as satisfaction in their lives and that’s the reason why we offer top quality auto parts brands to our customers. We make sure to provide a positive experience to our consumers from the brands which we are offering so that they can form an opinion that a particular auto parts brand is trustworthy and would give them peace of mind while they are purchasing it for their car. Here we have listed out some top brands for oxygen sensor.

Denso Oxygen Sensor

Bosch Oxygen Sensor

Delphi Oxygen Sensor

NGK Canada Oxygen Sensor

Richporter Technology Oxygen Sensor

Related Parts for Oxygen Sensor

It is always good to learn more! That is the reason why we are here to help you out in gaining more knowledge about car oxygen sensor. Here are some oxygen sensor related parts which would help you to understand it in a better way.


Total Costs & Repair Times, Effort For Oxygen Sensor

Failure in the oxygen sensor comes in a lot of forms. But take note that it is not an inexpensive repair. Sometimes in the end you might find out that there is a need of complete oxygen sensor replacement. There is no fast and hard number as to how much would a replacement would cost as it depends upon a lot of factors like the brand, make, model as well as the mechanic who is going to repair/replace it. The average cost for an oxygen sensor replacement is between $343 and $545. Labor costs are estimated between $64 and $82 while parts are priced between $279 and $463. Estimate does not include taxes and fees. This service is typically done as part of a bigger, more expensive repair, so the estimate you see above may not represent your total cost.

How to Change Oxygen Sensor?

It is important to understand the exact steps while replacing an oxygen sensor as it can cause damage to various components in the exhaust system.


A bad oxygen sensor (O2 sensor) can increase:


  • Hydrocarbon emissions
  • Carbon monoxide emissions
  • Oxides of nitrogen emission
  • Fuel consumption
  • And upset engine performance!

When replacing the O2 sensor always be careful not to damage the mounting threads on the exhaust manifold, pipe and the catalytic converter. Since the O2 sensor rarely malfunctions, its removal can be tricky. If the mounting threads get damaged, the repair cost will increase significantly. Thus, inspect, learn and then go for it.


Preparing to Remove the O2 Sensor


If the sensor is mounted on a flange, follow these steps:


  • Unplug the electrical connector.
  • Unscrew the mounting bolts.
  • Remove the old sensor.
  • Install a new unit along with a new gasket.

If the sensor is of any other type, follow these steps:


  • Few hours before trying to remove the O2 sensor apply a penetrating oil spray onto the sensor base where it joins the exhaust manifold.
  • After spraying, start the engine and let it idle for about 10 minutes. This helps the exhaust system to warm up for easy removal of the sensor.
  • Next, remove the black coloured negative battery cable and wrap it with a rag to avoid any accidental touch to the battery post.
  • If the sensor is close to the catalytic converter, you will need to lift the vehicle from the front. Use a floor jack to raise the vehicle from front and keep it in that position using some jack stands. Next, block the rear wheels with wooden blocks and apply parking brakes. Always make use of safety glasses to avoid dust or grease from entering the eye.

Removing the Oxygen Sensor


  • Unplug the sensor connector and avoid breaking the locking tabs.
  • Next, turn the sensor counter clockwise using an open-end wrench or a sensor socket.
  • If the sensor is frozen or stuck, cut the wiring harness and use six point deep well socket or a breaker bar instead.
  • Apply some more penetrating oil to the sensor base.
  • Again, turn the sensor a few degrees just until it doesn’t move anymore. Apply some more oil and tighten the sensor again. Repeat this step till the sensor gets removed easily. Don’t force into it.
  • After removing the sensor, apply the oil to the mounting threads and clean them with a nylon brush.
  • Check for any damages to the mounting threads and use a thread chaser to repair them. If the thread is crushed or stripped, use a tap to repair them.
  • After the repairs, clean the thread properly using penetrating oil and a clean rag.

Installing the Oxygen Sensor


  • Always check for the sensor specification before buying the new one. It should always match with the old O2 sensor. It is advisable to use an OEM unit rather than a universal one to avoid hassle.
  • Be careful of not contaminating the tip of the sensor with oil, grease or dirt as it sensor may not function properly because of it.
  • To prevent cross threading, always hand-start the sensor.
  • Using the sensor socket and torque wrench, tighten the sensor is accordance with the service manual.
  • Plug the sensor electrical connector and route the wiring away from hot surfaces.
  • Lower the vehicle, reconnected the negative charge cable to the battery and start the vehicle. Your new O2 sensor should now function properly.