Home TroubleshootingMotor Oil P0521 – A Bad Oil Pressure Sensor Or Something Else?

P0521 – A Bad Oil Pressure Sensor Or Something Else?

by Kelvin Yates

Have you gotten the check engine light and you’ve diagnosed the P0521 code? Well, if that is the case, then you are at the right place because, in this article, there will be a lot to cover when it comes to this OBD2 code and how to overcome it.

Having a problem with the check engine light can be a really frustrating thing. Mainly because it is there and you basically do not know what it represents. A lot of people are scared too much of it and some ignore it.

Frankly, you should not do any of these things. You need to be proactive when it comes to a problem and try to overcome it. Don’t be afraid of it, just focus on solving it. The important thing you need to do is to learn how to troubleshoot stuff and get a good grasp of the basics of car diagnostics. And that’s what we are going to cover in this article before we elaborate on the problem with the P0521 code.

First, we will cover the basics of car diagnostics where we will familiarize ourselves with the methods and tools needed for diagnosing a problem. Then we will cover the P0521 code meaning and understand more about it. After that, we will cover the causes of this code as well as the bad oil pressure symptoms since this component is mostly affected by this code. Later on, we will jump to diagnose and fix the problem. So, if you want to learn more, follow along.

Introduction To Car Diagnostics

Now before we dive into more complex stuff like the P0521 meaning, let’s first learn some of the basics when it comes to car diagnostics. I bet that there are a ton of people who are not into cars and are barely starting. They need a good introduction to this topic. If you feel like you are up to the task, you can move to the next chapter, if not, keep up with us for a bit.

Nevertheless, when it comes to car diagnostics, it is important for you to start thinking like a technician. Diagnostics is not something like removing a wheel and doing the brakes. When trying to solve problems, you need to think differently.

You need to focus on the causes and the symptoms of each problem. Then study all the possibilities and then draw a conclusion. This could be really confusing at the beginning but after you get into it, it will be a breeze to diagnose even the most complex problems in your car. And I mean really complex stuff.

The P0521 is a good thing, to begin with. Nothing too complex. So, if you have diagnosed this code with an OBD2 scanner, then you should focus more on understanding its meaning. After that, you need to move to the causes and symptoms of this problem and then move on to diagnose the matter.

And for this purpose, you will need to have an OBD2 scanner tool to get access to the codes. The second tool you will need will be a multimeter. You cannot go anywhere without a multimeter. Now in the next chapter, let’s elaborate more on the P0521 code meaning.

P0521 Engine Oil Pressure Sensor/Switch Range/Performance

Now as we covered the basics of car diagnostics and learned what kind of approach you should make when trying to tackle a problem of this kind. Let’s now focus on the P0521 Chevy Silverado code. What is the definition of this code?

The simple definition is “ P0521 Engine Oil Pressure Sensor/Switch Range/Performance”. But what does all this means in the first place?

Well, this means that there is a problem with your engine oil pressure sensor. This is a special sensor in your car that is tracking the oil pressure to let you know that you have a proper oil pressure going on in your system. In addition to this, it helps the PCM to adjust the work of the engine based on this data and also notify you if you have low oil pressure in the system.

So, you get the point and understand how important this device is. But is this problem serious?

Actually, it is not that serious because this sensor is only serving the purpose of monitoring things and not regulating stuff. So, you will be ok if you delay the repair a little bit.

But what is worth noting is that the oil pressure sensor isn’t always the one that can cause this stuff. Sometimes there could be something more that is going on in the system. And more about that we are going to cover in the causes section where we will elaborate more on the P0521 causes.

Engine Oil Pressure Sensor

So, we learned the basics of the oil pressure sensor and the meaning of this P0521 code. Now let’s elaborate more on this oil pressure sensor.

This engine oil pressure sensor is also known under three names. The first one is the engine oil pressure sensor, the second name is the oil pressure switch, and the third name is the oil sending unit. Whenever you hear these terms, don’t get confused, they are the same thing. They monitor the oil pressure in your engine.

What is worth noting is that this is a three-pin connector sensor. Meaning that the connector has three wires. A 5-volt power wire, a signal return ground, and a signal voltage wire. But where this sensor is mounted? Well, that’s what we are going to learn in the next chapters.

5.3 Vortec Oil Pressure Sensor Location

Now let’s cover the 5.3 Vortec oil pressure location before we dive into the P0521 causes. This is a fairly common engine so it deserves a separate chapter when it comes to the location of this oil pressure sensor.

And the exact mounting location for this engine is on the rear end of the engine. It is located right when the engine ends and gets close to the firewall. In most cases, in order to get to this sensor, you will highly likely have to remove the intake manifold if you don’t have the access to this sensor. So, it could be a pain to remove it.

Chevy 6.0 Oil Pressure Sensor Location

Now let’s cover the Chevy 6.0 oil pressure sensor before we dive into the P0521 causes. And when it comes to the 6.0 Vortec. It is worth noting that the mounting position of this oil pressure sensor is the same.

It is at the rear of the engine just where the engine ends. In most cases, you will have trouble removing it if you don’t have a special socket key angle extension. So, beware of this when trying to remove it. It could be really tricky to get a hold of it.

P0521 Causes

Now as we covered the basic meaning of the P0521 code and the mounting location of this oil pressure sensor. Let’s now take a look at the causes of this problem.

What could go wrong and cause the P0521? Let’s elaborate on all of the possible causes in the following chapters and learn more about them.

1. Faulty Oil Pressure Sensor

The first and most common cause for this P0521 code is a faulty oil pressure sensor. This sensor can fail in a number of ways and cause trouble for you as a car owner.

How this sensor works is really simple, there is a closed circuit. So, whenever you start the engine the circuit opens up and the oil light turns off.

This means that there is proper oil pressure inside the system. If the light doesn’t turn off, you probably have a bad oil pressure or the oil pressure sensor is faulty. This is why you need to further investigate the problems and learn more about this sensor and bench test it if needed to determine if the sensor is faulty or something else is causing the problem.

And when we are mentioning other probable causes for the P0521 code, let’s move on to the next chapter.

2. Faulty Wiring Or Connector Of The Oil Pressure Sensor

The second thing that could cause a P0521 code is bad wiring of the sensor or a bad connection to the sensor.

Whenever you have a problem like this, it is of utmost priority for you to inspect the wiring and the ground connection.

And for this, you need to check all three pins of the connector, the ground, the signal voltage, and a return ground. The signal voltage basically varies depending on the oil pressure that you have. 5V is the recommended voltage. Anything above or below the predicted values is going to trigger the P0251 code or a different code.

So, you need to make sure that all the wires work properly and you have a proper ground, and that there is no short in the electrical circuit. This is how you will be sure that you have proper working wiring. In addition to this, you will also clean the wiring connectors from corrosion and oil and make sure that there is good contact between the connector and the sensor. Now let’s move to the next probable cause.

3. Low Oil Pressure

The third most common cause for the P0521 code is a problem with the low oil pressure in the engine. Yes, that’s right, low oil pressure can easily trigger this oil pressure sensor and also cause a code like this.

It is worth investing your time to also see the level of the oil you are having. This will guarantee that your problem with the P0521 is not caused by low oil pressure.

This situation happens in engines that are worn out and have not been loved during their lifetime. So, if this is the type of engine you are dealing with, then you can assume that there could be low oil pressure and this low oil pressure is causing this problem.


The most common cause of low oil pressure is the oil pump. Most cars implement a wet sump system with an oil pump that picks the oil through the pickup tube from the bottom of the oil pan and then distributes this oil across the engine.

And what could happen is that this oil pump can fail and cause a lot of trouble for you like in this case with the P0521 code and the check engine light, and also the low oil pressure indicator. So, beware of this. Now let’s move on to the next probable cause.

4. Sludge Buildup

The last probable cause for the P0521 that we are going to cover is the problem with the sludge buildup in the system.

If you are a fan of overdue oil changes and you keep on delaying the service of your car, then it is highly likely that you will be having problems like in our case with the P0521 and problems with the oil pressure sensor.

The sludge will clog the screens of this oil sending unit and will cause it to malfunction. This sensor likes perfectly clean oil.

This is why you need to perform all the oil changes regularly and make sure that you avoid situations like this in the future. On some engines with a ton of sludge, even manual removal of this sludgy mess will be needed in order for these issues like the P0521 code or similar codes to appear. That’s why to change your oil frequently.

But what are the bad oil pressure sensor symptoms? Let’s elaborate on them next.

Bad Oil Pressure Sensor Symptoms

As we covered the causes for the P0521 code and we determined that the main cause for this problem is the oil pressure sensor.

I think we would all agree that now is time to discuss the bad oil pressure sensor symptoms. Knowing the symptoms will tell you quite a bit when it comes to this component and learning how to diagnose it properly. So, let’s get into the symptoms.

1. Check Engine Light + Oil Light On

The first in our list of bad oil pressure sensor symptoms is the check engine light + the oil light on. Since you are here you are probably aware of the check engine light because you diagnosed the P0521 code.


But another important thing is the oil light. The oil light could be on if there is a malfunction inside of this sensor. Or else, you might have to figure out how to reset the oil change light and how to reset the oil light, as well as how to reset oil life.

So, these two lights, or only the oil light will turn on and notify you that you are having a problem. The next step is to diagnose the problem with an OBD2 scanner and see what you get. If the P0521 code is one of these codes, then you know where to look for your culprit.

2. Oil Pressure Sensor Leaking

The second in our list of bad oil pressure sensor symptoms are the leaks that will come from this sensor in addition to the P0521 code.

As you probably know, whenever this component fails, it basically gets clogged up with oil and some of this oil pressure will try to escape from the component and try to get out of it through the wiring.

So, if you have some oil drops close to the oil pressure sensor or switch, then you know that you are dealing with a bad sensor. This is a clear giveaway that you need to perform a replacement of this component if you want to sort out your issue and not have problems in the near future with the check engine light and the P0521 code. Now let’s move to the last probable symptom.

3. Oil Pressure Gauge Low Or Too High

The last in our list of bad oil pressure sensor symptoms is the bad reading from the oil pressure gauge. Not all cars have this gauge but most of them do.

So, whenever you have a problem with the oil pressure sensor, the gauge for the oil pressure will go crazy. It will either show too high oil pressure or too low pressure.

This means that you will never get a proper reading from the gauge until you sort out this problem with the pressure sensor. This is why you need to further diagnose the P0521 GMC Sierra code and bench test this engine oil pressure sensor. And in the following chapter, we are going to explain how this procedure is done the right way at home. So, you don’t want to miss that.

How To Diagnose & Fix The P0521?

Now let’s move on to diagnosing the P0521 Chevy Tahoe code and oil pressure sensor and see what readings we will get. For this purpose, you will need a multimeter tool. With this tool, you are able to measure resistance, continuity, voltage, and other things in which we are not interested at the moment.

In our scenario, we are only interested in continuity and resistance. The first thing you will need to do is to set up this multimeter to measure continuity. Turn on the multimeter and set it to measure continuity. This is the setting where you get a beeping sound when there is continuity.

Then place one probe at the body of the sensor which is the metal part, then place another probe in the pin. This test will work with both single-pin and two-pin sensors with no problem whatsoever.

The only thing we need to hear is the beeping sound that tells us that we have continuity. The reading on the multimeter should be zero if we are dealing with a closed-circuit sensor that is in good condition.

The next test that we would want to perform is to check the resistance. It is basically the same thing. The only thing you need to do is to tweak the multimeter to measure resistance. Then you will get the reading. Most of the sensors are closed, so there should be close to zero resistance.

The third test basically involves a pressure test. For this test, you will need to have a compressor. So, it can get trickier to pull off. In the video above you can see how this test is performed on the sensor. Now let’s cover the cost to fix the P0521 Chevy Suburban code.

Cost To Fix The P0521

Now let’s cover the cost to fix the P0521 Chevy Silverado code. How much it will cost you to fix this problem on your Chevy or any other type of vehicle?


The diagnostics will probably cost you about $120 on average. If the sensor needs replacement, you will have to pay about $50 for the part and about $100 to $150 for the labor to replace it.


In this article, we have covered quite a bit when it comes to the problem with the P0521 code and the problems that arise from this code.

We learned what this code represents and what are the main causes as well as the symptoms. Then we moved on to diagnosing and learned how to bench test an oil pressure sensor.


Now let’s answer some frequently asked questions.

What Does Code P0521 Mean

This means that the PCM has detected a problem with the oil pressure sensor on your car. This is a problem that mostly affects this sensor or the wiring of this sensor. Both of them need to be checked if you want to resume driving with a proper working oil pressure gauge.

What Causes A P0521 Code

This code is often caused by problems with the oil pressure sensor or the wiring of this sensor. Mostly, by these two culprits. Other things can that can cause it are dirty engine oil, rare oil changes, and low engine oil.

How Do I Fix Code P0521

Fixing this code requires diagnostics to be performed. The oil pressure sensor and the wiring have to be checked and diagnosed if they are working well. Then move on to check the level of oil, the condition of the oil, and see if there is any oil sludge in the engine that prevents the sensor from working properly.

Can Low Oil Cause Check Engine Light

Yes, it can cause the check engine light to turn on. Cars are too smart nowadays not to detect a low engine oil. First, you will be greeted by the oil light and then the check engine light will turn on if you have a problem with this oil pressure sensor because of the low oil pressure.

Check Engine Light And Oil Light On At Same Time

This can happen if this oil pressure sensor detects that the engine does not have enough oil to run properly. The check engine light and the oil light will be triggered by the oil pressure sensor that will notice a lack of oil pressure in the engine and low oil in general.

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