P0134 – Is Your Car Suffering From A Bad O2 Sensor?

Have you performed computer diagnostics on your car and determined that you have the P0134 code on your car? If that is the case, then you are at the right place because there will be a lot to cover on this topic where we will learn everything on how to overcome this problem.

Having a problem like this can be a real pain because this type of problem nobody wants. The check engine light will basically going to light up and will haunt you until you repair it. You don’t want to enter and start your car and the first thing you will notice is the check engine light on the cluster.

This light is something that a ton of owners do not want to see and they just pretend like it is not there. But you shouldn’t be one of these people. Why I’m saying this? Well, this is the case because you have a problem with your car and this problem needs resolving. But you shouldn’t worry because we are going to help you out.

First, we will cover something more on the basics of car diagnostics and then we will discuss more on the O2 sensor and P0134 code which is closely associated with this sensor. Then we will cover the main causes of this problem as well as the symptoms associated with it along the diagnostics process and the repair guide. So, if you want to learn how to tackle this issue, follow along.

P0134 Code

Now before we jump into more complex stuff such as the P0134 bank 1 sensor 1 problem. Let’s take a look at the basics of car diagnostics first. I bet that there are a big number of people who are reading this article and want to learn something more about the basic stuff when it comes to car diagnostics. So, this chapter is dedicated to them.

When it comes to car diagnostics, the first thing you need to learn is the basic concepts of this practice. Modern car diagnostics is a lot different from diagnostics that were performed back in the day.

Modern cars implement a lot of tech and a lot more things can go wrong with them. Back in the day, everything was simple and easy to learn and understand.

But when it comes to modern cars, you just need to step up your game and learn how everything is connected first, and then once you have an understanding of how everything works. Then move on from there and learn how this component is diagnosed and fixed in the right manner.

In order for you to be successful at this work, you will need to get an OBD2 scanner. With this tool, you will be able to get access to the PCM which is the main computer.

This computer is controlling everything and also is storing DTC trouble codes. And since the P0134 code is one of these trouble codes, we are really interested in learning more about it in order to understand why it appears.

Once you have diagnosed the code and determined that you have a P0134, you concluded that one of the O2 sensors is faulty. And more on that in the next chapter.

What Is An O2 Sensor And How Does It Work?

As we cleared the basics of car diagnostics and the tool you will need to perform it. Now we can move on and cover another important topic for us. And that is the basics of the O2 sensor and how it works. Knowing this is essential when it comes to understanding the P0134 code. So, what is an O2 sensor? Let’s explain.

An O2 sensor is a component that is measuring the flow of oxygen inside of the exhaust pipe. This oxygen flow is really important for you when it comes to maintaining the air to fuel ratio.

And along with the MAF sensor, the O2 sensor has the job to read the data that it gets and send it to the PCM. Then the PCM based on the readings from these two sensors is to maintain the air to fuel mixture so your car runs the most efficiently possible. To learn more, check out our explainer on what does a mass air flow sensor do.

What is worth noting is that there are two of these O2 sensors. One before the catalytic converter and one after the catalytic converter. Having two of these sensors is a must in order for your catalytic converter to work at the optimal level and do its job as it should.

Whenever you have a problem with the O2 sensor, you are risking the life of your catalytic converter and you don’t want that since catalytic converters are really expensive components.

This is why it is really important for you to be able to tell if you have a problem with a certain O2 sensor like in our case with the P0134 code and fix the problem as quickly as possible. But have you asked yourself what is the meaning of this P0134 code? Well, more on that in the following chapter.

P0134 Bank 1 Sensor 1

Now as we understood what the O2 sensor does and why it is so important, now it is time to move on and learn the P0134 code meaning. What this code means and what is its definition?

The P0134 code is a generic code that is present on a ton of car makes. It doesn’t matter if you drive BMW, Chevy, Ford, Toyota, or Honda. The P0134 code is appearing on all cars. What is most important for you is the definition. And the definition of this code is “P0134 Oxygen Sensor Circuit No Activity Detected (Bank 1 Sensor 1)”. But what does all this means?

Well, this means that there is an interruption with the electrical circuit for the oxygen sensor for bank 1 sensor 1. This means that sensor 1 on the first bank is causing this trouble. But where is this sensor located in the first place?

Well, the P0134 bank 1 sensor 1 location is on the first bank. This bank is where cylinder number 1 is located. So, if you have an inline engine this cylinder should be the first one from the front or the left, depending on the engine layout. If you have a V configuration engine, you should consult your owner’s manual or online resources to find this bank.

Once you found the bank that is in charge of this sensor. You need to locate the sensor itself. This is the first sensor that comes before the exhaust manifold. So finding it is pretty easy. You will notice how it is mounted somewhere between the exhaust manifold and the catalytic converter. On inline engines, this sensor is even mounted on the exhaust manifold itself. Now let’s move to the causes of the P0134 code.

P0134 Causes

As we cleared the P0134 code and we learned what it represents. Now it is time to focus more on the causes of this code.

It’s the O2 sensor, right? Well, it can be the O2 sensor. But it also can be some other things that could trigger this code. And this is why we are going to list all of them so you get a better perspective when it comes to diagnosing this problem with the P0134. Now let’s begin covering the causes.

1. Broken O2 Sensor

The first and most common cause for this problem with the P0134 code is a broken O2 sensor. The O2 sensor can fail and stop working.

Whenever you get a message like this with no activity in the electrical circuit. Then this is one of the options that you should consider for this problem. But do not jump to conclusions too soon because there could be some other causes for this problem as well. And that’s what we are going to cover in the following chapters.

2. Blown O2 Sensor Fuse

Another very probable cause for the P0134 code is a blown fuse for this particular sensor. In the fusebox, there are fuses that regulate everything when it comes to the sensors and other components.

So, maybe one of these fuses has blown. And when the fuse is blown, you don’t have an electrical circuit. The connection is stopped. So, this is the second most common reason for the P0134 code and you should definitely consider it.

Open up the fusebox and locate the fuses for the O2 sensor on bank 1. Then if there are some of the fuses that are blown, you should replace them and hopefully fix your problem with this trouble code.

3. Bad Heater Element Inside Of The Sensor

The third most common cause for this P0134 code is a bad heater element inside of this sensor. Every O2 sensor has a heating element that helps the sensor to come up to operating temperature.

So, when this heater element inside of the sensor fails, it could trigger some of these codes. So, don’t be surprised when you notice the check engine light and this code.

What is important for you in this situation is to see if you have a bad heater inside of this sensor or not. And for this, there will be other codes that will help you out when it comes to determining this problem. Another thing that will be useful will be the live data that this sensor produces. And that is something that you can check with a more advanced OBD2 scanner tool. Now let’s move to the next cause for P0134.

4. Bad Wiring From The Harness To The Sensor

The fourth most common cause for the P0134 code is the problem with the wiring of this particular O2 sensor.

This sensor has wiring that travels from the wiring harness. Sometimes, this wiring can fail and when the wiring fails, you basically end up with a broken O2 sensor.

This could be attributed to a number of factors. More precisely heat, age, also damage done by rodents. Thus, it’s worth looking into how to keep mice out of your car. The wires can be cut and this will indicate that there is no power in the circuit.

So, it is often advised for you to check these wires to determine that indeed the wiring is in good condition and that there are no obstructions between the wiring harness and the sensor itself. This way you will rule out possible wiring damage that can cause the P0134.

5. Bad Connector

The next cause that we would like to cover for the P0134 code is the problem with the connector for the O2 sensor.

This connector is the one that connects the sensor to the wiring harness. Sometimes the connection can get loose if the plastic cracks around it and cause a no connection inside of the electrical circuit.

So, it is advised that you check the connector and see if the connections inside are nice and tight. If the connection is bad, you will have to replace the connector in order to sort out the problem with the P0134 code. Now let’s move to the last cause of this issue.

6. Broken PCM

The last thing that we would like to cover before we dive into the P0134 symptoms is the problem with the PCM.

The PCM as you probably know is the Powertrain Control Module. This is basically the car computer. Sometimes this PCM can fail and cause problems like these. When you have a situation like this with strange OBD2 codes popping up for no particular reason. One of the options that you want to take a look at is the PCM. Now let’s move on to the symptoms.

P0134 Symptoms

As we cleared all of the possible causes for the P0134 code, now we can take a look at the symptoms that you will experience when you are dealing with this type of code.

There are always causes and symptoms and knowing both of them will greatly help you when it comes to the diagnostics process and understanding the problem. So, let’s begin.

1. Check Engine Light

The first symptom that you will notice will probably be the check engine light. And you are also probably being aware of this light and this is why you are here.

But what is worth noting is that there could be some other codes as well when you are having an issue like this. Codes connected to this particular O2 sensor.


This is why you need to check them out as well before you make your decision on what could be the root cause of the issue. You just don’t want to make premature decisions. Sometimes when the PCM is faulty, there could be P0134 and P0154 in pair and this greatly indicates a problem with the computer. So, beware of these codes and check each code in detail.

2. Poor Engine Idle

The second symptom that you will probably notice when you experience a P0134 code will be a rough engine idle.

The engine will like to run really rough when you have an issue like this. But why is this the case? Well, this will be the case because the air to fuel mixture will be all messed up. When this mixture is bad, then you can expect the engine not to be happy at all.

So, the rough engine idle is one of the first symptoms that you will have when you also have the P0134 code. So, beware of it.

3. Hesitation Or Engine Stutter

The third most common symptom of the P0134 code is the engine hesitation and the engine stutter. The engine will not be happy at all whenever an O2 sensor is not working.


So, when you are dealing with a situation like this it is important to address it as soon as possible if you want to prevent this type of engine work and possible engine damage to be done.

4. Engine Stall On Idle

The next symptom of the P0134 code is also a really important one. This is the situation when the engine stalls on idle.

Without the O2 sensor in really good condition, you will have a ton of trouble running the engine. So, when the engine idles if you don’t press on the gas to give it a bit more throttle, it could easily stall on you.

5. Smell Of Gas And Blue Smoke

And the last symptom of the P0134 code is the smell of gas that you will notice when you have a problem like this.


The bad O2 sensor can make your car run rich and cause some smell of gas to be felt while running the engine. This is unburnt fuel that will be expelled from the exhaust pipe. This situation can be also detrimental to your catalytic converter, so be aware of it.

How To Diagnose & Fix P0134 Code?

Now as we cleared the causes and the symptoms of the P0134 code, now we can move on and start talking about how you can diagnose this problem and sort it out, hopefully. What you can do to fix this issue?

Well, the first thing you will need to do is to determine really if sensor 1 on bank 1 is faulty or not. But before that, you need to pop up the fusebox and see if there are problems with the fuses. Sometimes a fuse can fail and cause an issue like this.

The next thing you will need to do is to check the wiring from the PCM to the sensor harness connector and see if the contacts are working.

Then comes the testing for the sensor itself. You have to test this sensor with a multimeter to see if it is working or not. Without proper testing on the wiring and the sensor you are risking replacing a good sensor.

And for this, you will need to get a multimeter. With this multimeter, you can measure resistance, voltage, or continuity.

For this purpose, you will need to turn the multimeter to measure resistance. So, you will need the ohmmeter for this purpose. Good reading for a properly working sensor is somewhere between 2 to 4 ohms.

How you can do this task, you can check in the video that we attached above. It is worth noting that there are also other methods for testing and fixing this P0134 code, so it’s up to you to look for and study them. What is unfortunate is that there is no temporary fix for the O2 sensor. Which means that you will have to replace it.

Cost To Fix P0134 Code

The cost to fix this problem with the P0134 code really depends on the cause of the issue. If it’s a simple fuse, you will get away with $1 or less for a new one.


But if the problem is bigger, it will require computer diagnostics and this can be pricey. You could end up paying up to $120 to get it diagnosed. Then if the O2 sensor is bad, another $200 to $350 for O2 sensor replacement. So, overall, these are the costs.

P0134 Code Facts:

  1. P0134 is a diagnostic trouble code that indicates an issue with the oxygen sensor on the engine bank that houses cylinder #1.
  2. The oxygen sensor measures the oxygen and fuel in the exhaust to ensure the correct ratio and sends this information to the power control module (PCM).
  3. An insufficient amount of oxygen or fuel in the exhaust can cause the car to emit harmful pollutants (if you want to learn more, check out our guide on does my car have a catalytic converter).
  4. The P0134 code can be caused by a faulty heater circuit, broken or disconnected wires, corrosion in connectors, engine vacuum leak, or a faulty PCM.
  5. Symptoms of the P0134 code include the Check Engine Light coming on, poor engine performance, a rotten egg smell (aka my car smells like rotten eggs), and black smoke from the exhaust.
  6. Mechanics use an OBD-II scanner to diagnose the P0134 code and check for issues with the oxygen sensor and its wiring.
  7. Common mistakes when diagnosing the P0134 code include assuming the oxygen sensor needs replacing without ruling out other possible causes.
  8. While the P0134 code is not likely to prevent vehicle operation, it can decrease fuel economy and potentially cause damage to the catalytic converter.
  9. Repairing the P0134 code may involve inspecting and repairing damaged wires and connectors or replacing the oxygen sensor or PCM.
  10. Before replacing the oxygen sensor, it is important to rule out problems with the wiring and connectors, and to reset the fault code and test drive the vehicle to ensure the issue is resolved.


In this article, we have covered quite a bit when it comes to the P0134 code and what it means. Then we learned the causes and the symptoms of a P0134 code.

After that, we covered how you can diagnose and fix the problem and at what cost will this repair be possible.


Now let’s answer some frequently asked questions.

What Is Code P0134

This code means that there is no functioning electrical circuit inside the O2 sensor. The sensor is probably dead, the wiring is cut off, or the fuses for the sensor have failed and need to get replaced.

What Does Code P0134 Mean

This code means that there is no electricity in the circuit of this bank 1 sensor 1. The sensor has probably failed internally. Or possibly there is a problem with the wiring or the fuses that are associated with this particular sensor.

Where Is Bank 1 Sensor 1 Located

This sensor is located on bank 1. Bank 1 is the bank where cylinder number 1 is located. And sensor 1 means that this is the first sensor that comes after the exhaust manifold or in some cases it is mounted on the manifold itself.

Is Bank 1 Sensor 1 Upstream Or Downstream

This sensor is upstream since it is the first sensor. The first sensor is always upstream and the downstream is the second one that comes after the catalytic converter.

How To Fix P0134 Code

Fixing this code will require you to learn more about the wiring diagrams and how to test wires and different components. Which in our case are the fuses, the wiring, and the O2 sensors. You can do this testing with a multimeter and there are many different ways how you can pull it off. Then based on the findings you should go for the right solution.

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