P0325 – Has Your Knock Sensor Gone Bad?

by Conner Mckay

Have you started experiencing some weird noises from the engine and you diagnosed the P0325 code? Well, if that is the case and you are in this situation, then you are at the right place because there will be a lot to cover on this topic.

Having a problem like this is something that nobody wants. Why is this the case? Well, mainly because it could be really annoying to deal with it on a day-to-day basis first. Not to mention that this situation could also damage your engine in the long term.

So, you need to put up your sleeves and start working on a way to tackle this problem quickly and effectively. And by this, I mean that you need to improve your troubleshooting skills and learn how to think like an engineer. Only by doing this, you will be able to uncover problems quickly as in the case with the P0325 code. But you shouldn’t worry about it because we are going to help you out with your trouble.

First, we will cover the basics of car diagnostics and we will cover the things you need to know before you jump to diagnosing the issue. Then we will cover the knock sensor and the causes for the P0325 code as well as the knock sensor symptoms. Later on in the article, we will cover the diagnosing process as well as how to fix this issue. So, if you want to learn more, follow along.

P0325 Code

Now before we dive into explaining the P0325 code, let’s first cover the basics of car diagnostics. This is needed before we dive into the causes and the symptoms of this problem. We need to cover the basics before we explain complex stuff.

Modern cars are not like they were back in the day. Back in the day, everything was easy and there were not a lot of things that could break.

Through the years cars got more and more complicated and we started to experience issues like in our case with the P0325 code. Which indicates that we have a problem with one of our systems. More precisely a problem with a specific sensor.

So, we can say that there are a ton of different sensors that when can break they could cause a ton of issues like the check engine light and other different symptoms. But the check engine light should be your top priority.

At first glance, you wouldn’t have a clue about the reason why is this code appearing. This is why you will need an OBD2 scanner tool to access the computer of the car which is the PCM. After you get the car scanned with this tool, you will get the data that the car produces. Which in this case is the P0325 code.

You will probably get other codes and from here you need to start connecting the dots and see if these codes are a consequence of some other codes. Solving a problem with modern cars is like a puzzle. This is why you need to learn the definition for each code as well as the symptoms and causes to make the right conclusion. But you shouldn’t worry because we are going to cover that next.

P0325 Knock Sensor 1 Circuit Bank 1

Now let’s cover the P0325 code. More precisely the meaning of this code. As you probably know, each code has a definition and meaning of what this trouble code represents. So, let’s briefly discuss this code.

The definition for this code is “P0325 Knock Sensors 1 Circuit Bank 1” But what does all this means in the first place?

Well, this is the definition of the code. And the meaning behind this message is that you have a trouble code that indicates a problem with the knock sensor 1 that is located on the first bank. Even more precisely, the electrical circuit of this sensor is faulty and needs to be checked. The P0325 is also known as the knock sensor code.

This information can be a bit overwhelming but you shouldn’t panic at all. This is just a warning message that the knock sensor has started to malfunction but probably is not completely knocked out.

Also, the severity of the problem is considered to be relatively low and you could drive your car for a while before you go to a shop. But still, don’t delay this repair for too long. You just don’t want to do this because you risk some damage to the engine.

Not to forget the symptoms that you will experience when this sensor is not functioning properly. So, make sure that you sort out this issue with the P0325 code and make sure that you avoid some permanent damage to be done to your engine.

But what is this knock sensor in general? Many people are confused by this component and that’s why we need to explain this sensor and its role inside of the engine and learn why it is so useful.

What Is A Knock Sensor?

Now before we cover the causes for the P0325 code and elaborate more on them. Let’s first learn more about the knock sensor. What this sensor is all about?

Well, internal combustion engines are prone to knocking. These knocks are audible information that there is something wrong inside of the engine. Either this is because of a low octane fuel, bad ignition timing, bad air to fuel mixture, or possibly bad spark plugs.

It is the job of this knock sensor to detect these abnormalities in the work of the engine. This means that this sensor collects the data when the engine starts to knock for some particular reason and based on this reason, the sensor tells the computer that there are increased knocks inside of the cylinder.

So, based on this data, the computer adjusts the other values to prevent and eliminate the knock. Namely, it will adjust the ignition timing if the engine timing is off, or do another task that will prevent the engine knock.

Sometimes this is unavoidable to reduce completely the knocks like in a situation when you pour low-grade fuel into your high compression engine. But in most cases, the knock sensor does its job really well and eliminates the risk of engine damage.

It is worth noting that the number of knock sensors depends on how many banks your engine has.

If you are running an inline engine, you highly likely have one knock sensor. If you run a V6 or a V8 engine you probably run two of these knock sensors. So, if you got the P0325, you probably are running a V configuration engine and the knock sensor of bank 1 is malfunctioning. But what are the real causes behind this? Let’s elaborate on that one next.

Causes For The P0325 Code

Since we cleared the P0325 meaning and we have covered the knock sensor. We learned that this sensor is specifically designed to detect abnormal combustion into the engine and help the engine preserve itself under these circumstances by performing countermeasures such as adjusting the air to fuel mixture and adjusting the timing.

Now let’s dive even deeper and learn all of the different causes of this problem. We know that this sensor is the main cause. But there is something more to this problem and this is also worth covering. So, if you want to learn more on this, follow along.

1. Faulty Knock Sensor

The prime reason for the P0325 we can say is that it is a faulty knock sensor. Many people make this conclusion and diagnose that their knock sensor has failed. Which is not wrong by any means.

The sensor can fail internally and start to malfunction. It will not detect the knocks that your engine creates and your engine will start to become louder and louder.

No more dynamic adjustments of the timing and the air to fuel mixture will be performed on your vehicle. So, this will be expected.

But you shouldn’t jump to conclusions too quickly and you need to diagnose this sensor the right way. Only by doing so, you can be sure that indeed this sensor has failed you and you have to replace it.

Also, you need to learn the other causes for this problem with the P0325 code and see if the issue lies somewhere in between. And that we are going to cover in the next chapter.

2. Problems With The Electrical Circuit And Wiring

The second cause for the P0325 code can be problems with the electrical circuit of the sensor. We all live in garages that have a ton of rodents and these rodents could easily get into the wiring of the car and create a big mess.

So, it is often advisable to inspect these wires that go from the knock sensor to the wiring harness and make sure that the wires are in good condition. If they are damaged and created a short, you will have to either replace them or insulate them with proper tape.

Another very common cause can be the connector itself. The connector is exposed to the elements and the connections inside over time can get loose. Causing a bad connection and the circuit will stop working.

It is advised to check the connections and spray them with special fluid for electronics or alcohol and remove any rust with an ear pick. This will make sure that your contacts are in perfectly good condition and will work when the connector is plugged in. Now let’s move to the next probable cause for the P0325 code.

3. Problems With The Engine

The next probable cause for the P0325 code that we would like to discuss is the situation when you are having problems with the engine itself. And by problems, I mean real problems.

If the engine is knocking because of a rod knock or something then it is highly likely that it will alert these sensors and cause problems.


Also, not to mention that using a low octane fuel can also cause your engine to start knocking. The knocks can be so severe that the sensor will take a toll because it will not be able to adjust the engine work based on these conditions and you will have problems with this component as well. So, beware of these engine issues. Now let’s cover the last possibility when it comes to the P0325 code.

4. PCM Related Issues

The last thing that we would like to discuss when it comes to the causes for a P0325 code is the situation with the PCM.

If you didn’t know, the PCM is the Powertrain Control Module. This is basically the car computer that regulates everything on your car. This computer is also known as the ECU or ECM shortened for Engine Control Module.

This computer or module as would some people call it starts to show its downsides after long years of use. It is an electronic component and electronics fail when it gets old. So, you need to keep in mind that whenever there are some illogical problems and check engine light with a ton of codes including the P0325, we can assume that this problem could also be caused by a faulty PCM unit.

The only way to solve this problem will be to replace this unit. Something that is not budget-friendly and could cost some money. Now let’s discuss the knock sensor symptoms.

Knock Sensor Symptoms

As we concluded that the problem with the e P0325 code lies in the knock sensor of your car, now we can move on and cover the knock sensor symptoms. Knowing these symptoms will be beneficial for you when it comes to uncovering problems like this one on your car.

This is why you need to know the symptoms as well. So, if you want to learn more, follow along.

1. Check Engine Light

The in our list of knock sensor symptoms will be the check engine light. The check engine light is unavoidable when it comes to a problem like in our case with the bad knock sensor.

The PCM will record the information that is sent to it by the knock sensor and adjust the air to fuel ratio and timing to reduce the knocks.


But whenever you have a faulty knock sensor circuit like in our case, there will be a problem in sending this information to the engine computer which is the PCM. So, the PCM will start to test the connection with this sensor and if the tests fail, it will deem the sensor inoperable and show the check engine light.

In this case, when the sensor on bank one is affected you can get a P0325 code. Sometimes the sensors on bank 2 are affected and you can get a P0330 or a P0332 code. They are quite similar but for the other bank of your engine. So, keep this in mind, now let’s move to the next symptom.

2. Loss Of Engine Power

The second in our list of bad knock sensor symptoms that could develop along the P0325 code is the loss of engine power. But why is this the case?

Well, if you didn’t know, the knock sensor sends really important information to the car computer about the detonations inside of the cylinders.

So, when this information will not be available on the computer. There will be a loss of performance. The engine will not work at the optimum levels.

This means that the engine will not be efficient as it should be from the factory. So, you could face decreased fuel economy, poor engine performance, and overall loss of performance from the engine. That’s why you need to diagnose the P0325 code.

3. Increased Engine Knock

The last in our list of knock sensor symptoms that appear along with the P0325 code is the increased knocks from the engine.

The engine will knock a lot more than previously when this sensor was working properly. This will be the case because the engine will not get that crucial data from the knock sensor on how to prevent these knocks that develop from low octane fuel or something else and this will be represented as audible information.

So, whenever you have this code P0325, you shouldn’t be surprised if you notice that your engine knocks. But how you can diagnose a bad knock sensor? Well, that’s what we are going to cover next.

Knock Sensor Replacement

Now let’s learn how to diagnose and replace this P0325 code. We will go through the whole process in depth and we will learn how this is done the right way.

The first thing you will need to do is to start the diagnostics process with an OBD2 tool and see what codes you are getting. If one of them is the P0325, you just know that you are having an issue with the knock sensor on bank 1.

So, the next thing you will have to do is to locate the sensor on your engine. For this, you will need to go online and browse for diagrams of your engine and the location of this knock sensor. Once you found the knock sensor, you will need to remove the connector. And then you will need to get a socket wrench and remove the knock sensor. This sensor should come off as a single bolt.

Then the next thing that you will need to do is to check the wiring of the knock sensor. For this purpose, you will need a multimeter. You will need to make sure that you get the right voltage from the connector. You should also check the ground wires if they are good.

Next thing you will need to check the sensor itself and see the resistance. For this, you need to turn on the ohmmeter on the multimeter. Then place one probe at the connector and one on the other side of the knock sensor. A good sensor should report O.L on the multimeter. On how you can do this can check out the video that we attached. Or you can check the one from the Eric The Car Guy below. Lastly, clear all of the codes.

Replaced Knock Sensor Still Getting Code

In this situation, your new sensor is probably faulty or you haven’t connected this sensor properly. You need to make sure that you connect everything back together in the right way.

Another thing you need to do is to clear all of the codes that are appearing with the OBD2 scanner. Clear the P0325 and it should not repeat itself again.

Cost To Replace Knock Sensor & Fix The P0325 Code

The cost to replace the knock sensor is between $100 and $250. Knock sensors are not expensive after all. But the replacement of these sensors is. They can be quite tricky to find and replace, in most cases, you will need to have a long socket key.


The labor can cost a ton more money. More precisely about $200 or even up to $300 in some cases, so you need to be prepared for this.

Facts about P0325 Code: Knock Sensor Malfunction

  1. P0325 is an OBD2 diagnostic trouble code associated with the knock sensor circuit.
  2. It indicates a malfunction within the knock sensor 1 in circuit bank 1, triggering a Check Engine Light to be illuminated on the dashboard.
  3. This code may be seen with other knock sensor codes and lean condition codes.
  4. The common causes of P0325 code are a failed ECU, a failed knock sensor, open or short in the wiring harness, and electrical connection issues.
  5. Symptoms of P0325 may include Check Engine Light illuminating on, a slight lack of engine power, or no felt symptoms.
  6. A mechanic can diagnose P0325 by using a scan tool to check for any codes, noting the freeze frame data for each of these codes, and performing a road test to confirm the issue is present.
  7. They can also check for proper knock sensor operation while the engine is revved and test the resistance of the knock sensor.
  8. Common mistakes when diagnosing P0325 include overlooking the basics or not completing the diagnostic steps in order.
  9. P0325 is generally not a serious code and should be able to be driven without issue to a safe location once the malfunction occurs.
  10. Repairs for P0325 may involve replacing the ECU, repairing or replacing the wiring harness, replacing a faulty knock sensor, or repairing an electrical connection.

Conclusion On P0325 Code

In this article, we have covered quite a bit when it comes to the P0325 code. We learned the basics of car diagnostics and how it is done the right way.

Then we have covered the P0325 meaning and definition. After that, we learned more about the causes, symptoms, and the diagnostics process, lastly we learned how much it will cost you to replace this component.

F.A.Qs For P0325

Now let’s answer some frequently asked questions.

What Is A Knock Sensor

A knock sensor is a sensor that serves the purpose to record abnormal ignition inside of the cylinder. This situation is referred to as knocking. So, this sensor detects the knocking and then informs the computer that the car has a knock in a specific cylinder.

What Does A Knock Sensor Do

The knock sensor detects the knocks inside of the cylinders. Then informs the PCM that there is a knock, so then the PCM adjusts the timing of the engine as well as the air to fuel ratio.

What Causes A Knock Sensor To Go Bad

Well, we can’t be sure what causes it to go bad. It could be age, miles, low-quality parts, or all three combined. Anything could cause this. So, better get a quality part when replacing this sensor.

What Happens When A Knock Sensor Goes Bad

The check engine light turns on and the code P0325 will be present. Or another code depending much on which bank of the engine is affected.

What Does It Cost To Fix P0325 OBD

The average cost is about $350 with the parts and labor. It is more expensive because it requires more labor to get this sensor removed. Also, the part isn’t that cheap.

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