P0521 Engine oil pressure sensor or switch range/performance

Oil pressure sensor/switch range or performance

P0521 in short

P0521 means the oil pressure reading is outside what the engine computer expects. It can be a bad sensor or wiring, but it can also mean real low oil pressure from low oil or a pump fault. Check the oil level and have it inspected soon. Stop the engine at once if the oil light comes on or it knocks.

The oil pressure sensor or switch tells the engine computer how much oil pressure the engine has. The computer knows roughly what pressure to expect at a given speed and temperature. P0521 sets when the reading does not match, for example when it is too low, too high or does not change when it should.

Unlike P0520, which is a circuit fault, P0521 does not rule out a real oil pressure problem. GM bulletins link P0521 to a sticking oil pump relief valve, an oil pump jammed by debris, and a spun main bearing. Ford bulletins link it to the wrong sensor after an engine replacement and to an internal oil leak.

That is why the first steps are to check the oil level and listen to the engine, and why a shop should confirm real oil pressure with a mechanical gauge before replacing the sensor.

Most likely causes

  1. Low oil level or the wrong oil

    Common general cause
    Why it ranks here
    Low oil is a common, cheap-to-check reason for low oil pressure readings and warnings.
    What would change this
    Rises if the dipstick shows the level below the add mark or the oil change is overdue.

  2. Faulty or incorrect oil pressure sensor

    Common general cause
    Why it ranks here
    A failed sender or switch is a known cause of false readings. Ford also found that some replacement engines need a specific sensor, because the newer sensor is not backward compatible.
    What would change this
    Rises if a mechanical gauge shows normal pressure while the sensor reading is wrong, or if the engine was recently replaced.

  3. Sticking oil pump relief valve or jammed oil pump

    Supported by vehicle data
    Why it ranks here
    GM bulletins describe P0521 with no or low oil pressure from a sticking pump relief valve on 2019 trucks and an oil pump jammed by debris on the 2021 Trailblazer and 2020 Encore.
    What would change this
    Rises on those vehicles, or if a mechanical gauge shows low pressure with a full, correct oil fill.

  4. Worn or spun bearing, or an internal oil leak

    Possible — needs testing
    Why it ranks here
    Worn bearings lower oil pressure, and GM and Ford bulletins trace P0521 on some engines to a spun main bearing or a leaking oil gallery seal. This needs an engine teardown or pro testing to confirm.
    What would change this
    Rises if the engine knocks, or if pressure is low even with a good pump.

  5. Sensor connector or wiring fault

    Possible — needs testing
    Why it ranks here
    A poor connection can skew the reading enough to look out of range. GM's 2024 Trax bulletin includes a harness inspection for P0521.
    What would change this
    Rises if the connector is loose, corroded or full of oil.

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Park on level ground, turn the engine off, wait a few minutes, and check the oil level on the dipstick.

    Low riskTool: dipstick, clean rag

  2. Ask a dealer whether your VIN has a bulletin for P0521. Ford and GM have issued several.

    Low risk

  3. Have a shop fit a mechanical oil pressure gauge in place of the sensor and compare real pressure with the maker's specification.

    Best left to a shopTool: mechanical oil pressure gauge

    Warning:This means removing the sensor and running the engine with a gauge fitted. Hot oil can spray if a fitting leaks, and running with low pressure can damage the engine. Leave it to a shop.

  4. If pressure is low, a shop removes the oil pan to inspect the pump and bearings, as GM's bulletin describes.

    Best left to a shopTool: workshop

    Warning:This is engine repair work. Do not keep driving the vehicle while pressure is low.

Symptoms

  • Check engine light, sometimes with a low oil pressure message
  • Oil pressure gauge reads low, high or jumps around
  • Oil pressure warning light or low oil pressure message Gets more serious: stop and have it checked.
  • Knocking, ticking or rattling from the engine Gets more serious: stop and have it checked.

How to fix

  1. Park on level ground, turn the engine off, wait a few minutes and check the oil level. Top up if it is low.

  2. Ask a dealer whether your VIN has an open bulletin for P0521.

On your vehicle

Ford

  • 2018–2021 · F-150 · 3.3L

    Supported by vehicle data

    Ford SSM 50988: after an engine replacement, P0521 and a low oil pressure warning can come from fitting a sensor that is not backward compatible. Ford says to transfer the original sensor or fit the listed part. Also covers the Explorer 3.3L and Transit 3.5L. Whether the message is still current is not verified.

  • 2020–2023 · Explorer · 3.0L EcoBoost

    Supported by vehicle data

    Ford SSM 51764 traces P0521 or P0524 with a low oil pressure warning to an internal leak at the main oil gallery seal. Also covers the Lincoln Aviator. Whether the message is still current is not verified.

  • SSM-50988Status unverified

    P0521 and low oil pressure warning after engine replacement

    2018–2021f-150, explorer, transit · issued · NHTSA 10217832

    After an engine replacement on the 2018–2021 F-150 3.3L, 2020–2021 Explorer 3.3L and 2020–2021 Transit 3.5L, P0521 and a low oil pressure warning can appear because the newer sensor is not backward compatible. Ford says to transfer the original sensor or fit the listed part.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • SSM-51764Status unverified

    P0521 or P0524 with low oil pressure warning from an internal oil leak

    2020–2023explorer · 3.0L EcoBoost · issued · NHTSA 10238468

    An internal oil pressure leak can set P0521 or P0524 with a low oil pressure warning. Ford says to check main oil gallery tube alignment and replace the gallery seal. Also covers the Lincoln Aviator.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • SSM-47072Status unverified

    P0521 after a crank/no-start

    2018f-150, expedition · issued · NHTSA 10136593

    P0521 can set after a crank/no-start. Ford advises against attempting repairs if the root cause cannot be found. Also covers the Lincoln Navigator.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2019 · Silverado 1500

    Supported by vehicle data

    GM PIP5630 links no oil pressure and P0521 to a sticking oil pump relief valve or a spun No. 1 main bearing. Treat P0521 on these trucks as possible real low pressure. Whether the bulletin and its later revisions are still current is not verified.

  • 2021 · Trailblazer

    Supported by vehicle data

    GM bulletin A202302140 covers oil pumps stuck by foreign material on the 2021 Trailblazer and 2020 Encore, with P0521, P06DE or P06DD. Whether the bulletin is still current is not verified.

  • 2024 · Trax

    Supported by vehicle data

    GM PIP5932 gives a harness inspection and oil pump tests for P0521 on the 2024 Trax. Whether the bulletin is still current is not verified.

  • PIP5630Status unverified

    No oil pressure and/or P0521

    2019silverado-1500, express, suburban · issued · NHTSA 10156914

    A sticking oil pump relief valve or a spun No. 1 main bearing can cause no oil pressure and P0521. The bulletin says to remove the oil pan and, if the bearings are good, replace the oil pump. Also covers the GMC Sierra. Later revisions were not reviewed.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • A202302140Status unverified

    Oil pump stuck by foreign material, P0521, P06DE or P06DD

    2021trailblazer · issued · NHTSA 10177355

    Foreign material can stick the oil pump, setting P0521, P06DE or P06DD. The bulletin gives a screening test and oil pump replacement. Also covers the 2020 Buick Encore.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • PIP5932Status unverified

    P0521 harness inspection and oil pump testing

    2024trax · issued · NHTSA 10239183

    For P0521, GM gives a harness inspection and oil pump testing steps.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

  • P0520Engine oil pressure sensor or switch circuit malfunction

    Same system Common general cause

    P0520 is the circuit code for the same oil pressure sensor or switch. P0521 is the range or performance code.

  • P06DDOil pump pressure control not responding, as if stuck off

    Shares causes Supported by vehicle data

    GM bulletin A202302140 covers oil pumps stuck by foreign material on the 2021 Trailblazer and 2020 Encore, with P0521, P06DE or P06DD.

All Vehicle speed, idle control and engine electrical codes

P0521 questions

Can P0521 mean real low oil pressure?

Yes. It can be a sensor fault, but GM and Ford bulletins link it to oil pump problems, bearing damage and internal leaks on some engines. Have real pressure measured before replacing the sensor.

What is the difference between P0520 and P0521?

P0520 is a circuit fault in the oil pressure sensor or switch. P0521 means the reading is out of the expected range, which may be the sensor or real low pressure.

Should I stop driving with P0521?

Stop at once and turn the engine off if the oil pressure light comes on or the engine knocks. Otherwise check the oil level and get it inspected soon.

Sources and review

  1. 2023 Integra Owner's Manual: Indicator, Coming On/Blinking — American Honda Motor Co.
  2. What To Do If Your Engine Oil Pressure Warning Light Is On — AA1Car.com (Larry Carley)
  3. GM PIP5630: no oil pressure and/or P0521 from a sticking oil pump relief valve or damaged No. 1 main bearing (2019 Silverado 1500, Sierra 1500, Express, Suburban) — General Motors / NHTSA ,
  4. GM service update A202302140: engine oil pump stuck by foreign material, P0521, P06DE, P06DD (2021 Trailblazer, 2020 Encore) — General Motors / NHTSA ,
  5. Toyota Camry Owner's Manual (OM06291U, 2.5L A25A-FKS / 3.5L 2GR-FKS) — Toyota
  6. Ford SSM 50988: low oil pressure light and P0521 after an engine replacement, oil pressure sensor not backward compatible (2018–2021 F-150 3.3L, 2020–2021 Explorer 3.3L, 2020–2021 Transit 3.5L) — Ford Motor Company / NHTSA ,
  7. Ford SSM 51764: MIL and low oil pressure warning with P0521/P0524 from an internal oil leak (2020–2023 Explorer and Aviator 3.0L EcoBoost) — Ford Motor Company / NHTSA ,
  8. GM PIP5932: engine wiring harness inspection and oil pump testing for MIL with P0521 (2024 Trax) — General Motors / NHTSA ,
  9. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles
  10. Ford SSM 47072: P0521 after a crank/no-start event (2018 F-150, Expedition, Navigator) — Ford Motor Company / NHTSA ,
Last reviewed
Written by
Saurabh K.
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