7 Symptoms of a Bad Oxygen Sensor

Symptoms of a Bad Oxygen Sensor – The oxygen sensor (shortened O2 sensor) measures the amount of unburned oxygen in the exhaust gases as they exit the engine through the exhaust pipe.

The oxygen here refers to the oxygen that did not burn during the air/fuel combustion process.

It is one important component of your car’s exhaust system that relays information to a vehicle’s onboard computer for a good performance of your engine. 

This oxygen, alongside other gases like carbon, is usually produced in the internal combustion engine of the vehicle. The O2 sensor plays a major role in fuel monitoring, delivery and emission releases.

How Does an Oxygen Sensor Work?

The O2 sensor measures the quantity of oxygen in your exhaust and gives feedback to your car’s computer.

This information is now used by the computer to adjust the air/fuel mixture of your car engine.

The O2 sensor works by producing their voltage when they get hot and it has a Zirconium ceramic bulb on the tip of the O2 sensor that is plugged in the exhaust manifold.

The O2 sensor keeps track of the oxygen that did not burn during the original air and fuel combustion. After this oxygen must have been detected, the O2 sensor sends the information to the engine control module (ECM) which is the central computer that manages different systems in your car and communicates with the different sensors that are stationed within.

When the computer receives information about the oxygen level in the exhaust gases, it will then determine if too much or too little fuel is being consumed by the engine. If there is more air than fuel in the cylinder, the exhaust gases emitted from the combustion process will have more oxygen in them than normal.

When this situation has been detected by the O2 sensor, it transmits the information to the engine control module which will make proper adjustments and ensure that the air and fuel mixture in the engine will be at the best level for combustion purposes.

Symptoms of a Bad Oxygen Sensor

Symptoms of a Bad Oxygen Sensor

Check engine light illuminates in the dashboard

Illumination or blinking of the check engine light is one major sign that your O2 sensor is bad.

The O2 sensor influences the overall fuel and air combination process. When the sensor notices that there is less oxygen in the exhaust gases after combustion, the engine tries to adjust it.

However, in a situation where the O2 sensor is failing, the engine will not be able to detect this problem and this can lead to poor performance of your vehicle. When the engine control module detects a problem with the oxygen sensor, the check engine light begins to blink or illuminate.

Poor fuel economy

When your car begins to consume fuel more than it is supposed to, it is an indication that your oxygen sensor is bad because the O2  sensor is supposed to indicate when there’s more fuel than air present in the combustion cylinder and when excess fuel is being burned in the engine than needed.

Excessive consumption of fuel is a sign of poor fuel economy and this occurs as a result of the O2 sensor giving wrong signals to the system or not signalling at all.

However, there are other factors that may contribute to your vehicle’s consumption of more fuel than normal.

Failing emissions test

When the O2 sensor is bad, emission tests fail constantly.

An emission test checks your vehicle to ensure that it is not producing carbon dioxide above safe levels.

The O2 sensor which is stationed in the manifold of the exhaust system helps with emission control and if it is bad, the emission test will fail.

Rough idling engine and misfires

This implies that your engine is not running steadily when idle.

The normal revolution per minute (RPM) rate of an ideal vehicle is supposed to be below 1000 but in a situation where it gets to 2000 or 3000, it means your vehicle has a rough idling problem which can be a result of a bad oxygen sensor.

Also, when the O2 sensor is bad, your car will run roughly and misfire while idling.

Poor engine performance

Your engine performance can weaken if there is an abnormal combustion process in the engine. This abnormality often occurs when the O2 sensor is bad.

It is important to fix a bad O2 sensor on time to save yourself from unplanned expenses.

You can notice this poor engine performance while driving because your car will not give the same optimum performance as always.

In some cases, when you march the gas pedal, the acceleration will be limited or struggling.

Sulphur or rotten egg smell coming from the exhaust pipe

A broken O2 sensor could be the reason for the horrible smell emitting from your car.

However, the presence of excess fuel in the engine is the major reason for this rotten egg smell or sulphuric smell emitting from your engine.

Usually, this smell is intolerable and poses an air pollutant that calls for an immediate action.

Black smoke from the exhaust

An emission of black smoke from the exhaust indicates that there has been a problem during the combustion process in the car’s engine.

The O2 sensor must send information to the car’s control module on how to adjust the quantity of fuel and air for proper combustion. If the O2 sensor is bad, it will be unable to balance the proportion of air and fuel in the engine which will lead to improper combustion that will, in turn, lead to the emission of black smoke from the engine.

When Should I Replace My Oxygen Sensor?

An oxygen sensor is a very important component of a vehicle and needs to be replaced once it develops any fault or has been put in use for a certain period.

If you notice any of the aforementioned symptoms, it is crucial to replace your O2 sensor to avoid further damages to your vehicle and to ensure fuel efficiency.

A deteriorating or bad O2 sensor will not be able to give the necessary feedback to the control module and this will affect the performance of your car.

Without waiting for your O2 sensor to go bad completely, it is important to replace your O2 sensor every 60,000 to 90,000 miles which can be after one year, or more.

What is the Cost of Replacing an O2 Sensor?

The cost of replacing the O2 sensor depends on its problem.

Prices vary depending on the fault.

If it’s a case of a broken wire, the cost of repair is about $100-$200.

Replacing the oxygen sensor costs $200-$300.

Repairing a leaking exhaust costs $100-$200 and  replacing the catalytic converter costs $400-$2400.

The cost of replacing an O2 sensor also depends on the mechanic labor and the vehicle model.

The cost of the oxygen sensor can be within $100-$200 while the mechanic labor cost ranges from $50-$150 hourly.

Symptoms of a Bad Oxygen Sensor

FAQs about Oxygen Sensors

Can a deteriorating O2 Sensor lead to power loss?

Yes! Loss of power can sometimes be attributed to a deteriorating O2 sensor.

A bad O2 sensor sends wrong signals to the control unit and improper adjustments might be made in the fuel system which is not good for the vehicle.

Fuel combustion is important for the proper operation of the vehicle. Improper combustion will cause insufficient power for engine function which will cause the engine to misfire and lead to loss of power.

Does a bad O2 Sensor also cause sputtering?

Sputtering is a series of spitting or explosive sounds made by your vehicle while driving.

A sputtering engine shows that the engine is not achieving full combustion. A deteriorating O2 sensor disturbs the amount of fuel in the engine and this will cause your engine to sputter.

The O2 sensor helps in measuring how much or less the exhaust gases are during combustion and sends feedback to the control unit to balance the amount of fuel in the engine.

A bad O2 sensor will not be able to perform this task thereby causing the engine to sputter.

Can I continue to drive my car even if it has a bad O2 Sensor?

Yes, you can drive your car with a bad O2 sensor as long as your engine comes up.

Although driving will be sluggish and difficult, you can manage for a few days till you replace it. The possibility of a car shutting down due to a bad O2 sensor is rare because its main duty is to send signals to the control module to adjust fuel level and if the sensor is bad it will cause the engine light to blink.

However, it is not good to leave a faulty oxygen sensor for too long in a vehicle. A bad O2 sensor can trigger other problems that may lead to the malfunctioning of your vehicle. So, once it’s been established that you have a bad O2 sensor, make effort to replace it.

How many oxygen sensors does my vehicle have?

The number of O2 sensors varies from vehicle to vehicle.

Cars manufactured from 1996 have two or more oxygen sensors, some even have up to four oxygen sensors like modern vehicles with V-6 or V-8 engines.

Cars manufactured from this period onward are expected to have an O2 sensor located below the catalytic converter to monitor the working of the converter.

The first O2 sensor usually receives the signal and can read the second O2 sensor located close to the catalytic converter. It can detect when the catalytic converter isn’t working as it should.

Cars with a single exhaust pipe usually have two O2 sensors fitted on them while cars with double exhaust pipes will have a total of four O2 sensors fitted on each exhaust pipe.

What can happen to a vehicle if it has a failing oxygen sensor?

When your O2 sensor is failing, it will be unable to send signals or correct feedback to the control module which will make it difficult for your car to balance the ratio of fuel to oxygen.

Failure to balance this ratio will affect the smooth running of your vehicle.

Also, a failing O2 sensor affects the engine’s timing, combustion process, intervals and other vital functions of the vehicle. Your vehicle will become very sluggish or eventually stalls.

Do I have to replace all oxygen sensors at the same time?

It is best to replace all O2 sensors at once for better performance of your vehicle because both tend to wear out over time.

Although when one O2 sensor becomes bad, it doesn’t mean that others are bad as well, but there is always a tendency for the other O2 sensors to go bad in a while after the first one had gone bad. On this note, it is safe to replace all O2 sensors at once.

How long do oxygen sensors typically last?

Vehicles manufactured earlier have O2 sensors that can last 30,000 to 50,000 miles or 3 to 5 years.

Vehicles manufactured more recently have O2 sensors that will last 100,000 miles or 7-10 years. This however depends on how you maintain your car and engine. If your engine is properly maintained, your O2 sensor will last longer.

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