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Oxygen Sensor (O2) Symptoms, Function & Location

The oxygen sensor, also known as a lambda sensor, is located in the exhaust manifold of the car.

It measures the amount of oxygen in the gases leaving your car through the exhaust. Dr. Gunter Bauman created this sensor in the 1960s when he worked for the Robert Bosch GmbH company.

The sensor became famous and found a wide application in vehicles manufactured after 1980. The O2 sensor collects data from the gases leaving your engine and sends the data to the car’s central computer for analysis. The on-board computer ensures that your engine is in tip-top condition. So if it detects an irregularity in the exhaust gases leaving your car, it informs you in various ways.

o2 sensorBut like any other mechanical equipment, an oxygen sensor will eventually fail. If it fails, your vehicle will behave abnormally, but you will not know how to solve the problem if you do not know how to diagnose an oxygen sensor failure. We’re sure you’ll want to know that. That’s why we have prepared a list of symptoms and solutions to help you, which will give you valuable advice.

What is an Oxygen Sensor?

o2 sensor

The oxygen sensor is an electronic device that is installed in your car and measures the amount and concentration of oxygen in gas or liquid. It is also known as a lambda sensor. Advanced automotive technology is capable of producing the most efficient oxygen sensors. The lambda sensor is an essential component of all vehicles manufactured after the 1980s. The main function of the lambda sensor is to collect data on how much oxygen is available for combustion and send it to the engine management system.

The system then uses the data for fuel injection and other purposes. The oxygen sensor plays an important role in ensuring optimal engine performance and efficient fuel mileage. This sensor can also provide data on the emissions produced, and indicates when engine emissions are above standard limits using the CEL and oxygen sensor light. A poor or failed oxygen sensor will not only affect your car’s engine performance and fuel efficiency, but will also lead to incorrect emission measurements. As a result, you may get into trouble during an emission test or inspection because the emission tests would fail.

The oxygen sensor is required by your vehicle because your vehicle’s oxygen intake can vary for a variety of reasons, including air temperature, altitude of your vehicle, engine temperature, engine load, and barometric pressure. A defective oxygen sensor will not allow the computer to determine the air-fuel ratio for your engine. As a result, the readings are distorted, which affects the performance of the car. Oxygen sensors usually do not fail completely, but their efficiency decreases over time.

Oxygen O2 Sensor Symptoms

Cars can malfunction at any time, so you need to know when to see the mechanic. Here are a number of early symptoms that may indicate an impending failure of the oxygen sensors.

Check Engine Light Illuminates

The sensors are directly connected to the on-board computer of a car. The computer receives data from the sensors and evaluates it. However, if it receives incorrect data or no data at all, it triggers the check engine light on your dashboard. You may know by now that the check engine light can come on for various reasons; now you know that a faulty oxygen sensor can be one of them.

Poor Mileage

A bad O2 sensor distorts the tuning of the engine. Not only will the wrong amount of fuel be pumped into the system, but the air-fuel ratio will also be affected. As a result, more fuel is consumed and the mileage is reduced. If you are refueling more frequently, a faulty oxygen sensor could be the reason.

Misfiring Engine

A distorted fuel-air ratio will destroy the tandem inside the engine and its cylinders. This will lead to more backfires, black smoke rising from the exhaust and uneven idling. Among other things, the O2 sensor plays an important role in monitoring engine control and fuel supply, so if the sensor is damaged, your general engine condition will deteriorate.

oxygen sensorSolutions of a bad O2 Sensor

Fortunately, sensors are small engine parts that are easy to replace, but still we will look for ways to solve problems with O2 sensors without spending too much money.

Use an OBD2 Scanner

We cannot emphasize the use of OBD2 scanners enough. It is simply a vital tool for every car owner and a great tool for diagnosing car-related problems, especially when they involve sensors. This is because a sensor failure is usually reported to the car’s ECU, which lights up the check engine light. The only way to learn about the actual problem is to use an OBD2 scanner. The scanner will inform you about the exact problem, which you can later discuss with your mechanic. Sometimes the fault code can be reset and the problem disappears, which means you may not need to see your mechanic.

If you want to get an OBD2 scanner to use at home, you can check out this on Amazon: OBD2 Scannerir?t=askamastermec 20&l=am2&o=1&a=B078SQZ45J

Feedback Sensor and Voltmeter

These two things are required to test the oxygen sensor directly. Using a high impedance voltmeter and a feedback sensor, you can test the integrity of the O2 sensor while it is still attached to the car. All you need to do is check the wires surrounding the sensor and make sure they are in optimal condition. Once you have verified that, start the car and wait until it warms up. Place the voltmeter and check the sensor in certain settings. All this can be tedious for many of us, so it is better to take your car to the mechanic workshop. There you can get a clear diagnosis of the problem and find out if your sensor needs to be repaired or replaced.

Location of the Oxygen sensor

There may be several oxygen sensors on your vehicle. These sensors are located in the exhaust gas flow of your vehicle. One of the sensors must be located in front of the catalytic converter installed in the exhaust manifold. One or two sensors must be located behind the catalytic converter. This helps to monitor catalyst performance by comparing the before and after readings. These sensors can have different positions and numbers depending on the design of your car.

Oxygen sensor Replacement Cost

The average replacement cost of an oxygen sensor is between $200 and $260. The part can cost between $20 and $150, while labor costs vary between $90 and $250. The cost of replacing an oxygen sensor can vary greatly depending on the make of your vehicle and the labor required to repair it.

Based on reports from different areas and vehicle types, we have calculated an average range of the cost to replace the oxygen sensor. If you plan to replace the oxygen sensor yourself, you would usually only need to purchase the parts. The price of these parts can range from $20 to $150, depending on the make of car you own and where you buy it.

If you hire a technician or a mechanic to do the work, the total cost will vary greatly depending on how much the labor costs are to fix the problem. If you use a quality car repair shop, the cost is usually higher than if you have the car repaired by an independent mechanic. If you hire a mechanic to repair your car, he will charge you $90 to $250 to repair the problem in addition to the cost of buying parts. Because of such large price fluctuations, it is a good idea to do some market research and get several quotes from different mechanics. You can also ask people in your area who have recently replaced or repaired the unit.

Repairing/Replacing Oxygen sensor

The oxygen sensor is a small piece of equipment situated in a very sensitive area, meaning it can get damaged very easily. The wires surrounding the sensor are also prone to damage, so it is not unnatural to face oxygen sensor failure. Experts even recommend changing the O2 sensor after a few thousand miles just like you change the oil in your car. However, sensors can last a lot longer than oil, so you probably only have to empty your pockets after every 50,000 to 70,000 miles. This does mean that the sensor is not invincible: it is a mechanical part, which can only survive for so long.

Make sure you are visiting your mechanic for regular service and checkups so that total failure and replacement can be avoided. However, if you have no other choice than to change and replace your car’s oxygen sensor, it is wise to consider the many price alternatives.

Ones the oxygen sensor reaches the end of its life, the best option is to replace it in order to avoid continued trouble. In order to replace the oxygen sensor, here is what you need to do:

• Locate the oxygen sensor that you need to replace
• Consult the service manual of your vehicle to see where they are located in your vehicle design
• It should look like a spark plug sticking out of the exhaust pipe
• Disconnect the electrical connectors from the oxygen sensor
• Unscrew the oxygen sensor from the exhaust stream
• Match the old one and the new one
• Replace and install the new one from where you removed the old one
• Connect the electrical connectors that you removed
• Turn on the ignition without starting the vehicle
• Run the diagnostic scanner to clear the code
• Start the vehicle and observe any changes

In-Depth Diagnosis of a Failing Oxygen Sensor

Your vehicle can experience a number of changes if the oxygen sensor goes bad, and almost all of them will be negative changes. The check engine light is an important indicator for you to know that there is something wrong with your vehicle that needs to be taken care of, and it will light up in the case of a faulty oxygen sensor. Another sign that indicates a failing oxygen sensor is a message on the computer of your car which says that the heater circuit has malfunctioned. These two signs together mean that it could be a failing oxygen sensor. These signs can also be due to high emissions due to the poor performance of your car due to a different, unrelated reason. It’s often difficult to tell what causes some problems, so if in doubt, go see your mechanic.

Checking, testing, and diagnosing a defective oxygen sensor can be tricky and time-consuming. Therefore, it is better to simply take it to the expert mechanic and get it all done if you don’t have enough knowledge about it. If you are familiar with these things and have some prior knowledge, you can go about doing it easily. Here is a step by step guide that you can follow to carry out diagnostic tests for the bad oxygen sensor.

• Use a 10 megaohm digital meter to prevent any damage
• Locate the oxygen sensor using the service manual
• Use the service manual to identify the bad sensor with the help of diagnostic trouble codes (DTC)
• Choose the one among a number of sensors that you want to test
• Locate the Bank 1 and Bank 2 with the help of the service manual
• Locate the signal wire with the help of the manual
• Warm up your car with a 20-minute drive
• Turn off the engine
• Lift the vehicle with jack stands if required
• Get the voltmeter and set it to DC millivolt scale
• Avoid burning yourself and use protective wears
• Connect the red cable of the meter to the signal wire
• Connect the black with the engine ground or sensor’s ground wire if given
• Start your engine
• Read the voltage signals from the sensor on your voltmeter. It should be between 0.1 to 0.9 V
• If the values are over or under this range, this may be due to a bad sensor or engine performance.
• If improper values, test the oxygen sensor response to a lean fuel condition.
• Then test the oxygen sensor response to a rich fuel condition


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