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.

P0521 Symptoms

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

P0521 Causes

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

Code P0521 Severity – 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.

P0521 Diagnosis

  • Tools Needed to Diagnose:

Difficulty of Diagnosis and Repair

  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.

Was this post helpful?

Comments 7

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 !

en English