P0521 – Meaning, Causes, Symptoms, & Fixes

Code P0521 Definition

Engine Oil Pressure Sensor/Switch Range/Performance

What Does P0521 Mean?

The oil pressure sensor calculates the oil pressure of the vehicle’s engine. This is then communicated to the ECM in the form of a voltage value. The P0521 code is set when the ECM detects the voltage value is either higher or lower than the specified acceptable range of oil pressure. This code can also be set when the engine detects constant fluctuation of the oil pressure value.

What Are the Symptoms of Code P0521?

  • Check engine light
  • Oil pressure warning light
  • Oil pressure gauge too high/low
  • Engine stall

What Is the Cause of Code P0521?

  • Low engine oil level
  • Faulty oil pressure sensor
  • Disconnected wiring in oil pressure circuit
  • Disconnected wiring in EGR circuit
  • Engine failure

How Serious Is Code P0521? – Severe

Initially, this trouble code will not prevent your vehicle from regular operation. However, if not addressed early on, this code can cause serious internal damage to your engine causing complete engine failure. It is recommended to take your vehicle to the nearest dealership to have this code properly repaired to avoid costly repair(s).

Code P0521 Common Diagnosis Mistakes

Prematurely replacing the oil pressure sensor without visually inspecting the wiring of the oil pressure circuit for disconnection.

Tools Needed to Diagnose:

How to Diagnose and Repair Code P0521:

  1. Check to see if there are any other codes along with P0521 and clear your Check Engine Light with FIXD.
  2. Check the freeze frame data in an attempt to pinpoint the issue.
  3. Use the dipstick to check the oil level of your vehicle is sufficient.
  4. Verify the oil filter and drain plug are secure with no leakage.
  5. Visually inspect the wiring around the oil pressure sensor for disconnection.
  6. Check voltage of oil pressure sensor to ensure it is within specified range.
  7. If the problem persists, consider replacing the oil pressure sensor.

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Comments 14

Chester Parson

November 26, 2018

oil level was low. raised oil level to proper amount .erased code .SEEMS TO BE OK NOW.


May 1, 2020

What was the final thought. I have been having the same problem. Light came back on. The dealer changed the oil pump, sensor, screen and oil change. Was good for 1 year. 1 year and 1 month after the warranty expired. Light Popped back up. I changed the sensor myself this time. Light went away and came back up again. Oil level is good.

Jimy Fink

May 17, 2020

I’m having the exact same problems!


November 16, 2020

Hi everyone. I need help or advice. I recently had my check engine light on..I had code P0521. Changed oil pressure sensor to same factory one and the little filter also. 3 days later I have check engine light and it’s the same code. Oil level reads good on dip stick. Any ideas or suggestions?? Please. Thanks everyone.

Evertt Hurtado

September 14, 2020

Did your issue go away?


September 26, 2020

This code has made its ugly appearance whilst using my FIXD scan tool on my svz but my check powertrain warning is displayed on the dash computer next to my engine light can anyone confirm that the code and computer warning on dash are in direct relation to each other or am I looking at two different issues?

robert heness

November 26, 2020

i had a powertrain warning ended up being a fuel injector was faulty

Troy Nissen

November 3, 2020

Check your gascaps! You might just be surprised!!

Max Clubb

January 14, 2019

Took my car to my mechanic after using my FIXD to diagnose the check engine light which appeared very suddenly on my car. After FIXD showed a code of P0521, I took my vehicle to my mechanic. His sophisticated system showed the same code and the oil pressure pressure switch was replaced. Very happy that I purchased the FIXD and also purchased some for other members of my family. Thanks for an excellent product.

FIXD Marketing

January 14, 2019

That’s awesome Max! So glad we could help!


Darrell Simmons

February 14, 2019

I like fixd has been on point every time great to have

Oliver Nichols

March 18, 2019

Ran the synthetic oil passed the oil life mileage. Oil pressure reading about 20-25 psi. Changed oil and filter and oil pressure reading 40-50 psi. Removed code and has not come back.

Terry W Adams

May 7, 2019

Took my car to dealer. They replaced switch. Continued my trip. Stopped for gas and check engine light came back on as I accelerated to enter highway.


November 28, 2020

Po521 code on 07 trailblazer with 140k miles. Scanner says oil pressure voltage too high. Have changed sensor and screen, wire between ecm and sensor, changed oil and filter, oil pressure gauge in dash and still get 521 code. Vehicle runs great other than check engine light for oil pressure. Would pull my hair out if I wasn’t bald. Lol. Any ideas?

David Rickard

May 20, 2019

FIXD has been a big help to me as I do work on my Trail Blazer myself . Some were a pain but I adhered to fixing the problems at hand, a great product !

Timothy C Domer Sr

November 26, 2019

I have FIXD and had this error code pop up earlier this year on my GMC Sierra. I took it to the dealer and they ran diagnostics on it and came up with the same error. They replaced the sensor and did an oil/filter change. Nine months later I get the same error message again. It seems strange that the sensor went “bad” again so soon. Looks like I’m going back to the dealership again.


January 23, 2021

Terry, with my experience with these new generation engines. Their is an o ring at the bottom of your oil pump that connects the oil pump and pick up tube that goes bad and you won’t get the oil pressures that you should.


February 21, 2020

Just had my oil pressure sensor changed out including the filter that goes in there too light turned off and just came back on oil level is good what else could be the problem? 2013 Chevy Silverado 1500


April 27, 2020

I’m having same problem now what did yours end up being


October 23, 2020

Did you ever come up with anything? I have the same problem.


June 5, 2020

I have a 2013 GMC with same problem

Julian Gutierrez

July 21, 2020

Hi, Check engine light on my dash, replaced the oil pressure sensor along with the small filter on my 2012 Tahoe. The check engine light disappeared after replacing the sensor but after driving couple of miles it came back up again, I deleted it and after couple of days showed up again and never went away. Any suggestions please thank you…


October 23, 2020

Did you ever come up with anything? I brought it to the dealer. They charged me $500. It’s back on. They wanna do $1200 more of exploratory work with no idea if it will work I’m so frustrated.

Troy Nissen

November 3, 2020

Check your gas cap! You might be surprised!


December 27, 2020

Hi Troy: can you write more about what you mean by GASCAPSL do not understand what you mean google translates errors?
have the same error 521 on my Tahoe 2007 has change sensor / filter / oil
errors come again vh. leif Danmark cobenhagen


January 13, 2021

If p0521 keeps popping up, it’s not just a sensor or low oil level. Did both of those to no avail. Had to change my whole oil pump. While I was in there, changed out the rod and main bearings. I have split Year’07/‘08 GMC Sierra with the 6.0 Vortec Maxx. 2 years out, still running. I have almost 300k on this truck!


January 20, 2021

Awesome to hear, Darcy! Thank you so much fo this tip. Happy and safe driving! 🙂

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