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 8

Chester Parson

November 26, 2018

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

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.

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.

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