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P0521: Engine Oil Pressure Sensor/Switch Range/Performance

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Code P0521 is a generic OBDII fault code that indicates an oil pressure issue or problems with your oil pressure sensor. 

But is it a severe code? 
And what causes it?

This article will examine p-code P0521 in detail, including its meaning, symptoms, and fixes. We’ll also take a look at some other related queries and their answers

This Article Contains: 

Let’s get started!

What Is Code P0521?

Engine code P0521 is defined as the “Engine Oil Pressure Sensor/Switch Range/Performance” error code. 

This diagnostic code is a generic OBD-II powertrain code triggered when there’s a problem with the engine oil pressure or oil pressure gauge readings.

Note: Being a generic engine code, P0521 applies to all OBDII-equipped engines built after 1966. However, the causes and repairs may differ depending on the car model, and the mechanic will need to refer to your vehicle manual for assistance. 

What Does Code P0521 Mean?

The Powertrain Control Module (PCM) is responsible for most of your car’s computer system controls and sensors. One of these is the engine oil pressure sensor circuit. 

If the PCM senses any issues with the oil pressure sending unit, it pulls engine code P0521. 

In short, if your engine’s pressure voltage reading is too high or low or is rapidly fluctuating, you’ll see code P0521 turn up.

There are several reasons this could happen. Let’s take a closer look at them.

What Causes Error Code P0521?

One of the most common causes behind error code P0521 is a lack of proper vehicle maintenance. Not getting a frequent oil change or using low-quality oil can severely affect your engine’s oil pressure and result in fluctuations. 

Other than that, some other causes behind code P0521 are: 

So are there any signs to indicate diagnostic code P0521? 

What Are The Symptoms Of Code P0521?

The most common sign of diagnostic code P0521 is your Check Engine light turning on. A dashboard alert will likely accompany it. 

Your engine may also display some other symptoms. 
Here’s what you should look out for: 

In some cases, your OBD scan tool may read other P codes in addition to P0521, including P0520, P0522, P0523, and P0524.

But does that mean it is severe? 
Let’s take a look.

Is Code P0521 Critical?

On its own and with early diagnosis, P0521 is a moderately critical fault code. However, by no means should it be ignored.

Driving with low oil pressure can be very dangerous.
It may ignite your check engine light and require immediate attention. You may not even get any error code, but the oil pressure issue will affect your internal engine parts.

In worst-case scenarios, you may face engine failure. So, it’s best to regularly monitor your car’s engine oil pressure and oil level and get any P-code errors fixed ASAP. 

Before that, how is it diagnosed? 

How To Diagnose Code P0521?

As with all P-code errors, your mechanic will start their diagnosis with a visual inspection of the engine. They’ll check for the following things: 

After this checklist, your mechanic will check for any other p codes your engine may have pulled. This helps them determine any leaks within the oil pan, drain plug, or the sending unit.

Finally, your mechanic will check the oil pressure value using a mechanical oil pressure tester to ensure that it’s in the specified range. 

So now that you’ve diagnosed the problem, how do you fix it? 

How Is Fault Code P0521 Fixed?

Most times, once your mechanic has narrowed down the problem, they will perform the following repairs:

They will also compare your PCM’s engine oil pressure readings to another oil pressure scan tool. This will indicate whether there’s a problem with your PCM or oil pressure sensor. If that’s the case, you may need a new pressure sensor. 

Once the mechanic rules out the possibility of a problem with your PCM, they may need to replace and repair any damaged wiring and loose connections. This includes cleaning the oil pan and oil filter and replacing the sending unit, oil switch, or oil pump. 

Now that we have that out of the way, let’s look at other queries about fault code P0521.

2 Code P0521 FAQs

Here are a few queries about fault code P0521 and their answers: 

1. What Are The Mistakes To Avoid While Diagnosing Code P0521?

One of the most common mistakes made is prematurely replacing the oil pressure sensor without inspecting the wiring. It might be the case that there’s simply a loose connection or faulty wiring that is causing the low oil pressure.

There are also possible other issues, like a defective sending unit or oil pressure switch, or even a clogged oil pan. Perhaps your mechanical oil pressure tester or scan tool is giving out false readings. 

It’s, therefore, best to leave the diagnoses at the hands of professional technicians. Incorrectly diagnosing a fault code can cause further problems in the future. 

2. How To Replace Oil Pressure Sensors?

If you have a damaged oil pressure sensor that pulls a p-code despite no problems with your engine, you’ll need to change it. 

Here’s how:

  1. Locate the oil pressure sensor near the engine block or the cylinder heads and unplug the connectors. 
  2. Gently pull the electrical connector out of the sensor and then loosen the pressure sensor with a wrench. 
  3. Once you’ve unscrewed the sensor, simply replace it with the new sensor. Tighten the sensor into place by hand, and then use a wrench. 
  4. Reinstall the electrical connector. Be sure that the connectors sit fully and that the retaining tab is engaged.
  5. Start your vehicle and give it 5-10 seconds to build up the oil pressure value. Your check engine light and oil light should go away by now.

Note: Your car’s engine oil pressure sensor can be tricky to replace. It’s best to let someone with good mechanical knowledge have a look. They can determine if the problem lies with a low oil level, faulty wiring, or defective oil pump, oil filter, drain plug, or oil switch. 

Closing Thoughts 

Code P0521 can be quite severe if left untreated. But with proper diagnosis and repair, your engine won’t face a major oil pressure issue and should go back to running smoothly. 

The easiest solution to avoid triggering P0521 and other fault codes is to practice routine engine maintenance, including regular oil changes with the correct oil. 

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