Home TroubleshootingElectrical Bank 1 Sensor 1 – How To Locate This O2 Sensor?

Bank 1 Sensor 1 – How To Locate This O2 Sensor?

by Kelvin Yates

Have you diagnosed your car with an OBD2 scanner and you got a code that indicates a problem with the oxygen sensor for bank 1 sensor 1? And you don’t know how to find it? Well if that is the case, then you are at the right place because there will be a lot to cover on this topic.

Having a problem like this can be confusing because a ton of people who are not into cars will struggle to understand these things. They don’t know which bank is number 1 and which bank is number 2. And on top of that, a ton of people do not know where these sensors are mounted.

This is why we are writing this article to help you out when it comes to locating this sensor and hopefully helping you solve this problem. By reading this article, you will have a clear idea of where to look and how to pinpoint the exact sensor in a matter of minutes and not struggle for hours trying to figure out some simple things like these.

First, we are going to learn what is an oxygen sensor and how does it work. Then we will cover the bank 1 sensor 1 location and we will learn where it is located. But not only that, we will learn the location spot for all of the O2 sensors. Then we will learn more about the symptoms and how to diagnose and fix the problem. So, if you want to learn more, follow along.

What Is An Oxygen Sensor?

Now before we dive into the bank 1 sensor 1 location, let’s first learn some of the basics of the O2 sensor and learn what this sensor really is in the first place. I bet that there are a ton of people that are reading this and do not have the right understanding of this sensor and this and the next chapters are dedicated to them. So, let’s begin.

An O2 sensor in simple terms is a sensor that measures the flow of exhaust gases from the car. The O2 sensor basically is an electronic device that is measuring the amount of oxygen in the exhaust gases. This sensor is also known as the lambda sensor.

It was firstly patented by Bosh in the 1960s and since the late 80s is one of the most important sensors on our cars.

This sensor helps the internal combustion process and helps keep the car really efficient. So, whenever you get a malfunction on one of these sensors, you will basically face a ton of symptoms and poor engine work.

What is important for you is to know that you have two of these sensors on a single exhaust manifold. This means that there are sensor 1 and sensor 2.

This is why you are probably confused and you are trying to locate the right sensors on your car and the bank 1 sensor 1 confuses you even more. But you shouldn’t worry because we are going to help you out when it comes to this problem. First, let’s discuss more about how this sensor works behind the curtain, and then we will learn how many O2 sensors a car has and where is sensor 1 located.

How Does The O2 Sensor Work?

Now let’s take a look at how this O2 sensor works behind the curtain and understand more about its function. Then we will have the grasp of knowledge to start elaborating more on the location of bank 1 sensor 1.

So, how does this O2 sensor works? Well, this sensor is simply a probe that is installed onto your exhaust. The sensor is screwed into the exhaust pipe and there the sensor is exposed to the gas flow.

Once the gases start flowing into the O2 sensor, your computer will get the readings. So, why these readings are that important?

Well, they are because these readings help the PCM to adjust the air to fuel mixture in your car. This basically means that your car’s engine will be able to adjust all the parameters in order to work well.

Another important thing when you get trouble codes concerning this sensor is to know that inside of this sensor there is a heater element. This heater element heats up the sensor much quicker than relying on the sensor to heat up on its own.

Sometimes this heating element fails and you will start facing problems at startups such as rough idle and overall poor engine performance.

Also, when this sensor fails completely, you will also face problems with running the car properly. And in most cases, this problem will be so large that will prevent you from driving the vehicle.

So, when you get a P0130 O2 Circuit Malfunction (bank 1 sensor 1) you should not ignore it and try to solve this problem as soon as possible. But have you ever wondered how many oxygen sensors there are on a car? Well, that’s what we are going to cover next.

How Many Oxygen Sensors Does A Car Have?

Now before we learn the bank 1 sensor 1 location, let’s take a look first at how many oxygen sensors a car has? What is the exact number?

Well, the exact number of sensors really depends from application to application. The minimal number of sensors is two while the maximum number of sensors is four. So, why is this the case?

Well, this is the case because each bank of the engine on average has two sensors. These sensors are mounted in the exhaust as we mentioned.

One of these sensors is mounted before the catalytic converter while one of them is mounted after the catalytic converter.

Bank 1 Sensor 1

This is really essential because, in order for your catalytic converter to work at the optimum levels, you got to have two of these sensors.

There are engines that have two banks. This means that this bank is mirroring the first bank. It has all the same parts and the same number of O2 sensors.

So, in this case, they will be 4 in total in your car. Two of the O2 sensors are located on bank 1 and two of them on bank 2.

This is why the phrases bank 1 sensor 1 or bank 1 sensor 2 should not confuse you. But in the following chapters, we will further dissect these problems and learn more about the mounting locations of these sensors and how to locate them quickly and effectively. So, if you want to learn more on this, follow along.

O2 Sensor Locations

Now let’s cover the O2 sensor locations. Let’s elaborate more on where these sensors are located and how you can easily find them. More precisely how to find the first bank of your engine.

Once you located the number 1 cylinder, things will go pretty easy. So, we are going to explain that in detail in the next chapter where we will elaborate more on bank 1 sensor 1 location.

Bank 1 Sensor 1 Location

Now let’s get to business and learn more about oxygen sensor bank 1 and the bank 1 sensor 1 location. But where this bank 1 is located in the first place?

Well, the exact location of bank 1 is where the first cylinder is located on your car. So, how you can locate the first cylinder in your engine?

Well, this greatly depends on the engine manufacturer. Sometimes the bank one is on the left side, sometimes it is mounted on the right side. It greatly depends on the carmaker and their ways of engineering.

Usually, the first bank cylinder is a bit forward than the cylinder mounted on the opposite side. Cylinders simply cannot be an exact mirror because this design will not work.

So, the first cylinder always is a bit forward than the second cylinder that is first on the bank 2. Your best bet when it comes to your specific engine is to look at online diagrams for your engine. Look for the engine code and then try to locate cylinder number 1. On some engines, there is even a stamp that says “1” before the first cylinder.

But what about the bank 1 sensor 1 location? Let’s say that you presumably located bank 1 of your engine. Where is the location of the first O2 sensor?

The location of the first O2 sensor is right after the exhaust manifold. This means that the first sensor comes before the catalytic converter. Congratulations, you’ve located the bank 1 sensor 1 on your car. Now let’s move on to the bank 1 sensor 2 location.

Bank 1 Sensor 2 Location

We learned where is located bank 1 sensor 1 now let’s learn more about the bank 1 sensor 2 location. Where is sensor 2 located in your car?

Well, as you can notice, this sensor is also located on the first bank of your engine. But what is different with this sensor is that this sensor is mounted right after the catalytic converter.

What is good with this sensor is that it is more easily reachable and easily replaceable when necessary.

This is because the catalytic converter does not have to be removed from the car as in the case with bank 1 sensor 1. Now let’s move on to the next sensor location.

Bank 2 Sensor 1 Location

As we covered the bank 1 sensor 1 and bank 1 sensor 2. Let’s now move on to the bank 2 sensor 1 location.

As you can presume with the first two sensor locations that we covered, this sensor is located on bank 2 of your engine.

This means that you have to locate cylinder number 2 in order to determine on which side is this sensor located.

As we explained previously, on cylinder number 1 there is a stamped number 1 in most cars. So, it is easy to tell. But on some cars, you do not have this information.

So, it will be up to you to look online and try to locate cylinder number one. Just browse online your engine code and the cylinder numbers. You will probably get a ton of results on where this cylinder number two is located.

Also, you can rely on the common knowledge. Usually, the first cylinder is a bit more forward than cylinder number two. So, it is really easy to tell which side is bank 1 and which side is bank 1. But where is this bank 2 sensor 1 located?

Well similarly to bank 1 sensor 1, this sensor is located before the catalytic converter. This means that it comes in front of the catalytic converter. So, it is really easy to find it. Now let’s move on to bank 2 sensor 1 and learn more about the location of this sensor.

Bank 2 Sensor 2 Location

As we covered the bank 1 sensor 1 location and the location of the other sensors, the last on our list is the bank 2 sensor 2 location. Where this sensor is located?

Well, as we mentioned previously, you will first need to locate the bank 2 of your engine where cylinder 2 is located.

Then move on from there. First, you will see the bank 2 sensor 1, and then after the catalytic converter, you will notice sensor 2. It is that easy.

You only need simple logic and also a ton of diagrams online if you want to always find where these sensors are located without an issue. So, don’t be afraid of doing proper research and locating the sensor by studying a ton of pictures and videos online specifically for your engine.

Especially if you drive a mainstream car, there will be a ton of information out there that is waiting for you to dive deeper and learn more about the sensor 1 location. But is the sensor 1 upstream or downstream? Let’s cover more on that next.

Bank 1 Sensor 1 Upstream Or Downstream

Another question that bothers a ton of people that we would like to answer when it comes to bank 1 sensor 1 is if this sensor is upstream or downstream?

The answer to this is quite logical. The bank 1 sensor 1 is located before the catalytic converter. This means that this sensor is located upper than sensor 2 on the same bank.

So, we can conclude that sensor 1 is an upstream sensor. This sensor is in the first line of defense and it gets really hot. So, it can fail more often than the sensor that is located after the catalytic converter.

Imagine now that you have a bad bank 1 sensor 1, in this scenario, you will be exposed to a ton of symptoms. So, how can you tell if your sensor 1 is broken? Let’s elaborate more on that next.

Symptoms Of A Bad Oxygen Sensor Bank 1 Sensor 1

Now briefly let’s discuss the symptoms that you will face when you are having a bank 1 sensor 1 problem with your engine. What are the symptoms of a bad oxygen sensor? Let’s elaborate.

The first problem that you will probably face in this situation when you are dealing with a bad O2 sensor is the check engine light.

More precisely in our case, it will be the codes P0130 or P0135. The first one is concerned with the electrical circuit. While the latter is concerned with the heater element of this sensor. The heater element as we explained is allowing this sensor to reach the proper working temperature and allow the sensor to function properly once you start your car.

Bank 1 Sensor 1

Other symptoms that you will face will be associated with poor engine work. The sensor will not be able to give the right data to the PCM. So, the PCM will not be able to properly adjust the air to fuel ratio and you will end up with a ton of problems like lean or rich air to fuel mixture.

These situations will be associated with rough engine idle, frequent misfires, poor fuel economy, and overall low engine horsepower.

The car will not be happy at all and you will have a hard time driving this vehicle. So, when it comes to these codes it is important for you to find this O2 sensor which is located on bank 1 sensor 1, and then bench test this component. Only by doing so, you will be able to properly diagnose the problem. And in the following chapter, we are going to explain how it is done the right way.

How To Diagnose And Fix The Bank 1 Sensor 1?

Now let’s move on to diagnosing the problem with bank 1 sensor 1. How you can diagnose an issue with this sensor?

For this purpose, you will need a tool that is known as an OBD2 scanner. This tool will basically allow you to gain an access to the PCM and then scan the car for codes.

Once you got access to the computer of your car, you probably will be greeted by a few codes. If between these codes are the P0130, P0135, or a similar code close to these ones, then you highly likely are having a problem. Either with the sensor itself or possibly with the wiring of this sensor.

And here comes the tricky part. You will need to learn how to bench test this sensor and learn how to measure the values with a multimeter. For this, you will need to remove the sensor and then connect two alligator clips to the connectors.

Once the connectors are well connected, you can move on and diagnose the sensor. Turn the multimeter to measure volts and then heat up the sensor with a propane torch. Remember to heat up only the probe and not damage some of the wirings.

After that when the sensor gets really hot, you will be able to get some reading from it. The voltage should gradually increase if we are dealing with a good sensor and it should also drop after you remove the propane heat. How this is done on the bank 1 sensor 1 you can check in the video above. Now let’s move to the costs involved in this work.

Cost To Replace The Sensor?

Now let’s discuss more on the cost to replace this sensor, how much you can expect to pay in order to fix the bank 1 sensor 1?

Well, on average, a new O2 sensor costs somewhere between $250 to $350. The part alone is that expensive. While the replacement costs will also be somewhere in the range of $100 to $150. This is not cheap but it has to be done if you want to sort out the problem with the sensor 1 on your car. Now as we covered everything you need to know, let’s move on and conclude this article.


In this article, we have covered quite a bit when it comes to the bank 1 sensor 1. First, we learned what an O2 sensor is in general and what purpose it has. We understood that this is a crucial component that is really important for your car to operate well.

Then we learned the mounting location for all of the O2 sensors on your car with the primary focus on the sensor 1. Then we covered the symptoms of a bad O2 sensor and how to diagnose and fix the problem


Now let’s answer some frequently asked questions.

Which O2 sensor Is Bank 1

This sensor is the one that is located on the side of cylinder number one, so when you try to locate this sensor make sure that you find cylinder number 1 first. This way you will not make a mistake while locating this component.

Where Is Bank 1 Sensor 1

This sensor is located on the first bank of your engine. This is the bank that has the cylinders 1,3,5. The specific sensor that you are looking for is the one that comes before the catalytic converter.

Where Is Bank 2 Sensor 1 Located

This sensor is located on the second bank of your engine. More precisely the bank that has the cylinder number 2. So, you need to locate this specific bank and see which is number 1 and which is number 2. We are looking for number two in this case and the sensor before the catalytic converter.

Where Is Bank 1 Sensor 2 Located

Sensor 2 is located on the first bank of your engine. More precisely this is the sensor that comes after the catalytic converter. Locate the number one cylinder specifically for your engine and then look after the catalytic converter to find it.

You may also like

Leave a Comment