O2 Sensor Cost – How Much To Replace An Oxygen Sensor?

by Conner Mckay

Your car has a lot of sensors that feed information to the computer to keep it running smoothly. One such sensor you might not know of is the O2 or oxygen sensor. This is a sensor that sits in your exhaust system and monitors the level of oxygen inside your car’s exhaust gases. For such an important component, it’s not a surprise then that the O2 sensor cost isn’t inexpensive.

As with any other car part, the O2 sensor can fail over time. So how much does the O2 sensor cost? Expect to pay anywhere between $100 -$500 for a replacement. We’ll elaborate further below, and discuss everything you need to know about the O2 sensor cost.

O2 Sensor

O2 Sensor Cost

Before we get to the O2 sensor cost, let’s learn more about what the O2 sensor is and how it works. This will give you a better understanding of why they are important and why you should care about them. As mentioned, the O2 sensor is a sensor that monitors the amount of oxygen in your car’s exhaust gases.

Some manufacturers and mechanics will also call it the oxygen or lambda sensor. The sensor sits before the catalytic converter, and the catalytic converter itself is a device that filters the car’s exhaust gases to less toxic gases. But what is the O2 sensor for exactly?

The O2 sensor feeds the O2 amount information to your car’s Engine Control Unit (ECU). The ECU uses this information to calibrate how much fuel it should put into the engine.

If the O2 sensor detects there’s too much oxygen in the exhaust gases, the ECU will assume it’s running lean (less fuel, more air). It will then feed the engine with more fuel to balance out the mixture inside the engine’s cylinder.

It needs to do this as the engine needs to run on a balanced mixture of fuel and air. If the mixture is too rich (more fuel, less air), your car will consume more fuel and the car can emit a strong gas smell (to learn more, do head over to our explainer on how to get gas smell off hands and why does my car smell like gas). Meanwhile, a lean air-to-fuel mixture will result in misfires and popping. If left untreated, this can result in damage to the engine.

As you can see, while the O2 sensor’s job is quite simple, it actually plays a big role in keeping the engine running smoothly. A faulty O2 sensor won’t be able to feed the ECU with the correct information. This will disrupt the ECU’s ability to calibrate the fuel injectors and put in the right amount of fuel.

What Does An O2 Sensor Do

Most cars usually have two O2 sensors. One that sits before the catalytic converter (upstream), and one that sits after the converter (downstream). Here’s how they work:

Upstream O2 Sensor

The downstream oxygen sensor measures the oxygen level in exhaust gases coming from the exhaust manifold. The oxygen sensor works by producing voltage when they get hot, usually around 600°F and it has bulbs inside and outside the exhaust manifold. When the outside of the bulb is exposed to hot gases, the difference in oxygen level will cause the voltage to flow through the bulb.

When there’s a lot of oxygen, the voltage is going to be low. This tells the ECU that the fuel and air mixture is lean. Meanwhile, if it detects a low amount of oxygen, the voltage is going to be high. This tells the ECU that the fuel and air mixture is rich, and it will make the appropriate adjustment.

The ideal mixture is usually around 14.7 parts air to 1 part fuel, and in this scenario, the oxygen sensor will produce 0.45 volts. At this voltage, the ECU will assume the fuel and air mixture is correct and will keep the engine running that way.

Downstream O2 Sensor

The downstream O2 sensor works the same way as the upstream sensor. And ideally, it should also produce about 0.45 volts. The only difference is that it measures the gases coming out of the catalytic converter. The catalytic converter should maintain the ideal fuel-to-air ratio (14.7 air to 1 fuel), also known as the stoichiometric ratio.

The purpose of the downstream O2 sensor is to make sure that the catalytic converter is working properly. Most modern cars made after 1996 should have both of these sensors, and they are required to have at least one sensor.

But if you drive an older car before 1996, it’s possible that your car doesn’t have an O2 sensor. And yes, some cars that feature carburetors also have O2 sensors. They usually have O2 sensors if the car has electronically adjustable jets to control the fuel and air mixture.

Bad O2 Sensor Symptoms

While the O2 sensor’s job is simple, it does play a big role in the car’s operation. As such, you will definitely notice some symptoms when the O2 sensor goes bad. Here are some things you might notice when your O2 sensor is faulty:

1. Check Engine Light Is On

The check engine light is your car’s way of telling you that there’s a problem with the powertrain system. And yes, there are literally hundreds of things that can trigger the check engine light.

So if you see it, you’ll have to scan your car’s OBD with a scanner to find the error codes. These error codes will then be able to tell you what’s wrong with the car and you can narrow down the root of the problem from there.

We’ll guide you on how to diagnose your car using an OBD scanner. But for now, we remind you please do not ignore the check engine light regardless of what triggered it. You should try to find what the problem is and fix it before it gets serious.

And if your check engine light is flashing, then stop driving immediately. This means that there is something seriously wrong with your car, and continuing to drive will result in expensive and severe damage. You should tow your car instead to avoid damage.

2. Performance Loss

As mentioned, your car needs to run on a stoichiometric fuel ratio. This will ensure optimum performance and consumption. A faulty O2 sensor won’t be able to feed the ECU with the correct information. As a result, your car’s ECU can’t calibrate the fuel injectors properly.

The O2 sensor might be telling it there’s not enough oxygen even though there is and your ECU wouldn’t know any better! As a result, the engine won’t get the correct fuel and air mixture.

When this happens, engine performance will be affected. A slightly rich mixture may actually generate more power, while a lean mixture will result in a loss of performance. But either way, this isn’t the ideal way for your engine to run and you shouldn’t ignore a performance loss. Especially if your engine is misfiring.

Misfiring is when one or more cylinders aren’t combusting the fuel and air mixture at the correct time. This will feel like the car is hesitating when you accelerate, and the RPM isn’t running as smoothly as usual. It may also result in a popping sound coming from the engine. In any case, a misfiring engine is not normal and you’ll need to check it.

O2 Sensor Cost

3. Worse Fuel Economy

A faulty O2 sensor may tell the ECU that there’s too much oxygen in the mixture even though there isn’t. When the O2 sensor thinks there’s too much oxygen, the ECU will inject more fuel into the cylinders to balance out the mixture. In this scenario, your car will be using more fuel when it isn’t necessary and you will notice the fuel economy drops.

If you think your engine is using more fuel, you can verify this by paying attention to your exhaust pipes. When the engine is running a rich mixture, it won’t be able to burn all of the fuel that’s injected into the cylinders.

Unburned fuel will result in black smoke coming out of your exhaust pipes. If you see black smoke, your engine is putting too much fuel into the cylinders. You should check your car regardless of what the reason might be.

Other possible culprits include a faulty MAF (Mass Air Flow) sensor and MAP (Manifold Absolute Pressure) sensor. However, the most likely culprit is the O2 sensor. This is why understanding how to scan your car’s On-Board Diagnostic (OBD) system is important, as it will help you to narrow down the problem.

4. Rough Idling

If your car is burning a rich fuel and air mixture, it can also result in rough idling. Cars will normally idle below 1,000rpm without the air-conditioning running. Usually somewhere around 800rpm.

If your car is running higher than that or the RPM needle is jumping up and down erratically even when the engine is at optimum temperature, this is likely because of a rich fuel mixture.

5. Difficulty Starting

Another red flag of a potentially failing O2 sensor is difficulty starting the car. A problematic sensor can disrupt the engine’s air-fuel mixture balance. This may make it challenging for your car to ignite the fuel in the combustion chamber properly, leading to hard starts or even no start situations. It’s imperative to address this symptom swiftly, as it can lead to more extensive engine problems down the line.

6. Pungent Exhaust Smell

Be on the alert for unusual odors from the exhaust. A malfunctioning O2 sensor might cause the engine to run rich consistently, leading to an excessive buildup of unburnt fuel in the exhaust system. Consequently, this will produce a strong, pungent gasoline smell from the tailpipe. While it’s tempting to disregard a mere scent, this symptom could be a telltale sign of an oxygen sensor gone awry.

7. Uneven Acceleration

As you drive, pay attention to how your vehicle accelerates. An erratic or jerky acceleration pattern might indicate a misbehaving O2 sensor. As the sensor feeds inaccurate data to the engine control unit (ECU), it can cause abrupt changes in fuel delivery and ignition timing, making your vehicle’s acceleration unpredictable. Not only is this uncomfortable for the driver and passengers, but it’s also potentially dangerous on busy roads.

8. Engine Pinging or Knocking

Engine knocking or pinging sounds should never be ignored. These noises occur when there’s premature ignition of the air-fuel mixture in the combustion chambers. A faulty O2 sensor might misguide the ECU, leading to an incorrect air-fuel mixture that’s prone to pre-ignition. This condition, if prolonged, can severely damage the engine’s internals.

9. Reduced Engine Power

While you may already be familiar with the loss of performance due to an erroneous fuel mixture, a faulty O2 sensor can also result in a clear decrease in the engine’s power output. This could manifest as the car feeling sluggish, especially under heavy loads or during uphill climbs. It’s essential to remember that consistent running under such conditions might lead to accelerated wear and tear on your engine.

10. Failed Emissions Test

Regular emissions tests ensure that vehicles aren’t releasing excessive pollutants. A malfunctioning O2 sensor can cause your engine to produce higher levels of harmful emissions than permitted. Consequently, if your vehicle fails an emissions test, it could very well be due to a compromised oxygen sensor. This not only harms the environment but also could be costly if your state imposes fines or restricts vehicle usage based on emissions.

11. Visible Signs on the Spark Plugs

Your spark plugs can tell a lot about your engine’s health. If you suspect your O2 sensor might be malfunctioning, inspect your spark plugs. A failing sensor can cause a rich or lean mixture, leading to spark plugs with sooty-black or blistered white deposits, respectively. Both conditions can reduce the lifespan of your spark plugs and affect overall engine performance.

12. Strange Noises from the Catalytic Converter

The catalytic converter plays a crucial role in reducing harmful exhaust emissions. However, consistent rich fuel mixtures, often resulting from a faulty O2 sensor, can lead to the converter overheating or becoming clogged. This might produce a rattling or roaring noise, especially during startup or acceleration. Addressing this issue promptly is crucial as a damaged catalytic converter can be quite pricey to replace.

In summary, the O2 sensor, despite its modest size, plays an integral role in your car’s performance and health. By remaining vigilant for these signs and symptoms, and addressing any issues promptly, you can ensure the longevity of your vehicle and its components.

Oxygen Sensor Cost

O2 Sensor Cost

So, now you know how the O2 sensor works and the signs of a faulty O2 sensor. But how much does the O2 sensor cost? The cost will vary depending on your car’s make and model.

On average, expect to pay somewhere between $100 – $200. For example, an oxygen sensor for a 2010 Toyota Camry will cost about $169. However, the O2 sensor cost in some cars may be as low as $50.

Meanwhile, the labor cost for an O2 sensor replacement job is usually somewhere around $60 -$75. So, the cost for an O2 sensor replacement can be as high as $275. Of course, luxury and performance cars may cost more as there’s usually a markup. But in general, expect the total O2 sensor cost to be somewhere between $150 – $275.

Can You Drive With A Bad O2 Sensor

Well, yes, but you shouldn’t. As mentioned, a faulty O2 sensor can affect the fuel and air mixture in your engine and affect how it runs. If it’s too lean or too rich, or the engine misfires often, this can result in overheating. And needless to say, overheating is bad for your car.

Over time, this will lead to more severe damage. Overheating can cause damage to the pistons, and con-rods, and even cause cracks to develop on the engine block. When this happens, you will need an engine rebuild.

Depending on the severity of the damage, this can cost anywhere between $1,000 – $6,000. But one thing is for sure: damage to the engine’s internal parts will cost you a lot of money. Suddenly, that $300 O2 sensor cost doesn’t seem too steep.

So yes, you should replace your O2 sensor if it’s faulty.

How To Test O2 Sensor

We’d like to note that the labor cost for an O2 sensor replacement is relatively inexpensive. So we recommend you leave it to a professional mechanic and save you the time and trouble of replacing the sensor yourself.

With that being said, replacing the O2 sensor is not as difficult as you think. So, if you still want to save some money, or you need something to do on the weekend, we’ll guide you on how to replace your car’s O2 sensor.

But first, let’s make sure that the O2 sensor is actually the problem. We always like to verify what the root of the problem is first. There’s no point spending time and money on a repair only to find out that it wasn’t the root of the problem.

As mentioned, a faulty O2 sensor is likely to trigger the check engine light. If the light is on, you can scan your car’s OBD system with an OBD scanner to find out the exact cause.

1. Choosing An OBD Scanner

First, you’ll need to get a hold of an OBD scanner. An O2 sensor fault is likely to trigger a check engine light, and an OBD scanner will help you verify the problem. Your car has tons of sensors that monitor the engine’s operation.

When something is out of the ordinary, it will try to fix the problem by making whatever adjustments are possible. If the problem can’t be fixed, it will register an error code in the OBD system which in turn triggers the check engine light. The OBD scanner will find these error codes.

Keep in mind that there are OBD1 and OBD2. Cars made in 1996 and after will use an OBD2 system, and you will need an OBD2 scanner. So be sure to check what type of OBD system your car has and get the appropriate scanner. If your car has an OBD2 system, don’t worry about compatibility. OBD2 is universal and any OBD2 scanner will work on any car, regardless of the make and model.

There are several types and brands of OBD2 scanners that you can choose from. From traditional ones to Bluetooth scanners that can connect to your smartphone. But we recommend getting one of the traditional units, such as the Ancel AD310. Whichever you choose, they should be no more than around $100 at most.

Some advanced ones can cost thousands of dollars, but those are meant for professional car technicians and we don’t recommend you splurge on that. Once you get a hold of the OBD scanner, here’s how you scan your car’s On-Board Diagnostic system:

2. Scanning The OBD System

  1. Plug the reader into the car’s OBD port. This port is often located underneath the dashboard area, either above the pedals or your knee. Keep in mind that some cars might have their port hidden out of sight, such as in the engine bay. Check your owner’s manual or online to see where it’s located in your car.
  2. Once plugged in, turn on the OBD scanner. It should immediately scan the car. However, some scanners might require you to input additional information such as make, model year, VIN, etc.
  3. It will then display the error codes it has found. A more complicated scanner might also display a description of what’s wrong with the car, but if you have a simpler scanner then it’s recommended to take note of the codes displayed.
  4. Crosscheck what the error codes mean and research what might cause it.

3. Possible O2 Sensor Error Codes

There are literally hundreds of error codes that your OBD system can register. Here are some O2 sensor-related codes that you might see:

  • P0150 – P0155. These error codes mean there’s a problem with the upstream O2 sensor. It can be because of a broken sensor element, shorted wiring, or the sensor has been disconnected. In any case, the O2 sensor is likely to be faulty and you will need to replace it.
  • P0156 – P0167 also indicates something wrong with the O2 sensor, but this time with the downstream sensors. Possible causes include a broken sensor element, a sensor installed with incorrect heater current values, and shorted wiring.
  • P0170 – P0175. These error codes indicate incorrect fuel mixture and trim in the engine, and they indicate which bank is experiencing this issue. In any case, if you see any of these error codes, you have an incorrect fuel mixture. However, you will still need to find out exactly what’s causing it. Aside from the O2 sensor, a vacuum leak, fuel pressure or delivery problem (or the fuel pump low pressure symptoms), or a faulty MAF sensor can also cause this problem. If these codes are accompanied by the P0150 – P0167 codes, then this verifies you have an O2 sensor problem.

Those are pretty much the error codes you will see if you have an O2 sensor problem. We can’t list down what each one of them means, but this will be enough as a general guide.

If you don’t see the codes your car is registering, then you have a different problem. You’ll be able to find plenty of information on what those error codes mean online and find the appropriate solution.

How To Replace O2 Sensor

So, once you verify the O2 sensor is the problem, now you’re going to want to replace it. Surprisingly, O2 sensors aren’t that difficult to replace. Here’s how:

  1. The first thing you need to do is locate where the O2 sensor is located. It’s usually located somewhere in the engine bay, and you should be able to find the exact position in the owner’s manual.
  2. Disconnect the electrical connection to the O2 sensor. Follow where the O2 sensor cable leads and it will end in a plastic plug. Unplug the connector before removing the sensor.
  3. Since the O2 sensor still has wires, it will be easier to remove it using an O2 sensor socket, it’s specially designed to go around the O2 sensor wires and makes removing it a lot easier. Remember to use the correct size, and use penetrating oil like WD-40 if necessary.
  4. Get the new sensor and make sure it’s the correct part. Add a small amount of anti-seize to the thread, but don’t get it onto the tip of the sensor. New oxygen sensors should come with a bag of bronze gel, this is the anti-seize and it acts as a lubricant.
  5. Insert the new sensor and hand-tighten it. Then use the socket to fully tighten the new O2 sensor in place.
  6. Plug the electrical connector into the car’s plug.
  7. Start your car and see if the symptoms have disappeared.

Resetting The Check Engine Light

A check engine light may require a reset to get rid of it. If you’ve replaced the O2 sensor and don’t see any of the symptoms anymore, then you can reset the check engine light. Here are some ways to do it:

  1. Take the car for a drive. If it’s not gone after about 10 minutes, you’ll need to try other methods.
  2. Turn the ignition on and off three times in succession. In some cars, this will reset the computer.
  3. Disconnect the battery for 15 minutes, then reconnect it. Then see if the check engine light persists.
  4. If all fails, clear the error codes by using the OBD scanner. Scan the OBD system, and your OBD scanner should have the option to clear these error codes. Clearing these error codes should get rid of the check engine light.

Remember, only reset the check engine light if you’re sure that you’ve fixed the problem. If the check engine light returns, then that means you haven’t fixed the problem and you will need to find out what’s causing it again. At this point, we recommend taking it to a professional if it feels like too much effort.

O2 Sensor Cost: In Conclusion…

So, the O2 sensor is an important sensor that helps your ECU determine how much fuel it should put into the engine’s cylinder. A faulty O2 sensor will feed the ECU with inaccurate information and the ECU won’t be able to calibrate the fuel and air mixture properly. This will then result in an engine that runs either too lean or too rich and won’t run smoothly and possibly lead to damage.

The O2 sensor is relatively inexpensive, most O2 sensors will cost around $100 – 200, and it can sometimes be as low as $50. Additionally, they’re actually pretty easy to replace and you can do it yourself to save money. Hopefully, this post has been helpful and helped you to solve your O2 sensor problems.

O2 Sensor Cost: Frequently Asked Questions (FAQs)

If you’re still curious to learn more about an O2 sensor cost to replace, our FAQs here might help…

Where Is The O2 Sensor Located

The primary role of the O2 sensor is to measure the amount of oxygen left behind in the exhaust fumes. Therefore, the most ideal placement for the O2 sensors would be around or in the exhaust system of your car. Older cars tend to only have one oxygen (O2) sensor. However, to ensure maximal efficiency and data collection, modern cars often have two or sometimes more O2 sensors. Usually, there are upstream and downstream O2 sensors. The upstream sensors can be found near the engine, commonly by the exhaust manifolds, before the catalytic converters. Meanwhile, the downstream sensors are found by and after the catalytic converters.

What Does A Bad O2 Sensor Look Like

If the O2 sensors have gone awry, there are numerous symptoms that are indicative of its poor condition. Most often, bad O2 sensors prompt the check engine light to appear, as an alert from the ECU that something’s gone wrong. And, that it’s also stored some error codes for you to thoroughly diagnose a bad O2 sensor. Faulty oxygen sensors also cause other symptoms to show up, such as poor performance, poor fuel economy, rough idling, cylinder misfires, and black smoke from the tailpipes, among others. When your car gets a regular emissions check-up, you would also fail this test, owing to the malfunctioning oxygen sensors.

How Much Is An Oxygen Sensor

Replacing an oxygen (O2) sensor is relatively inexpensive, for the most part. The sensor itself can cost as low as $50, and you can skimp on labor costs if you opt to have it replaced yourself. On average, even with a professional replacement job at the local workshop, it shouldn’t cost more than around $100 to $200 for an O2 sensor replacement. A select few cases might see it skyrocket past this, though. For instance, the O2 sensor in some cars might be tougher to access. Or, you might have to replace more than just a single O2 sensor, if the condition worsens. If so, then you may have to spend upwards of $500 in a worst-case scenario.

What To Do After Replacing Oxygen Sensor

Once you’ve replaced the oxygen (O2) sensor, it’s wise to not immediately go off on a drive as per usual. Experts recommend that you plug an OBDII diagnostics scanner into your car. Then, use it to scan and reprogram, while also resetting your car’s central computer management system, the ECU (engine control unit). In doing so, that ECU can now re-learn and re-calibrate itself to the new O2 sensors. Furthermore, you’re allowing the ECU to receive updated information, sync, and optimize properly with the new sensors. This reset process is crucial to ensure that the ECU could interact as efficiently as possible with the new sensors.

Can An O2 Sensor Cause A Misfire

Yes, a malfunctioning and faulty oxygen (O2) sensor may cause a misfire, among many other possible tell-tale symptoms. This is so, as O2 sensors are responsible for letting an ECU know just how much oxygen there is in the exhaust fumes. Thus, allowing the ECU to properly manage the engine’s air-to-fuel ratio to ensure optimal performance. But if the O2 sensors go awry and send incorrect oxygen level readings and information back to the ECU, a misfire may occur. That’s because the ECU may falsely compromise the air-to-fuel ratio, leaving one or more cylinders unfired, and causing an overly lean or overly rich air-to-fuel mixture to be present.

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