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Proper engine oil pressure is required to keep your engine running. It ensures that all the moving parts within the engine are lubricated well to avoid wear. Excessive or insufficient oil pressure means that there is something wrong.

The P0521 code is one of the trouble codes that denotes a potential problem with the engine oil pressure switch or engine oil pressure. If your code reader or scanner registers it, read this comprehensive guide to learn about its meaning, probable causes, common symptoms, and more.

oil pressure sensor
Code P0521 indicates an anomaly in the engine oil pressure readings registered by the powertrain control module (PCM).

What Does the P0521 Code Mean?

Diagnostic trouble code (DTC) P0521 stands for “Engine Oil Pressure Sensor/Switch Range/Performance.” It indicates an anomaly in the engine oil pressure readings registered by the powertrain control module (PCM).

A vehicle’s oil pressure sensor is typically a three-wire sensor with 5 volts, a signal return ground, and a signal voltage that varies with engine oil pressure. The sensor’s job is to detect and report engine oil pressure to the PCM. The OBD-II code P0521 is triggered when the PCM perceives that the reading from the oil pressure sensor is higher or lower than predicted.

The P0521 engine code may point to a faulty oil pressure sensor, but it can also indicate insufficient oil pressure. And on vehicles with timing chain tensioners that operate with engine oil pressure, the oil pressure is even more critical than on a standard engine. For example, on a 3-valve Ford, if the oil pressure drops as low as 24 psi (usually because of worn camshaft saddles), the timing chains will usually begin to rattle because the tensioner isn’t doing its job. In some cases, the low oil warning light will illuminate.

If the low oil warning light activates along with the check engine light, stop driving immediately and have your vehicle towed for repairs. If this situation is unaddressed, it may lead to complete engine failure.

What are the Possible Causes of the P0521 Code?

Many issues can trigger the P0521 engine code. Below are just some causes of this trouble code. Note that since there are a lot of causes, you need a proper diagnosis to address the issue correctly and efficiently. When in doubt, consult a mechanic or technician.

  • Low engine oil level
  • Low oil pressure because of internal engine wear
  • Defective oil pressure sensor
  • Disconnected or faulty wiring in the oil pressure circuit
  • Defective oil pump
  • Incorrect oil filter (see “Other Notes” below)
  • Sludge buildup inside the engine restricting oil flow
  • PCM problems (e.g., outdated software)
oil filter
An incorrect oil filter can cause code P0521.

What are the Common Symptoms of the P0521 Code?

There are several telltale signs of the engine code P0521. If you’re dealing with this specific trouble code, your vehicle may exhibit more than one symptom listed below.

  • Check engine light is on
  • Oil pressure warning light is on
  • Oil pressure gauge reading is too high or low
  • Engine stalling
  • Engine noise

How to Diagnose the P0521 Code

Proper diagnosis for OBD-II trouble codes is essential. However, because of the number of causes for each code, including P0521, it can be quite a challenge. Below are some video resources you can use to get an idea on how you might diagnose the P0521 code:

How to Fix the P0521 Code

If you aren’t well-versed in automotive repair, it may be best to let your mechanic deal with the P0521 code. The process of fixing this DTC varies not only depending on what triggered it but also based on the affected vehicle’s make and model. For instance, the solution for a P0521 code in a Toyota Camry may not work for a P0521 code in a Chevrolet Silverado.

Diagnosis is the first step to resolving the P0521 code. Once you’ve established what set off the code, determine its appropriate fix by consulting online auto repair resources and guides. You can also sign up for an ALLDATA single-vehicle subscription for in-depth factory repair information.

Other Notes About P0521

The technical service bulletin (TSB) SB-10059078-4342 came out on August 2015 and addressed concerns with the P0521 code appearing on several vehicles equipped with a V8 Engine (RPOs L20, L77, L94, L96, L9H, LC8, LC9LH9, LMF, LMG, LY6, LZ1):

This TSB addressed concerns about the low oil pressure light being activated along with the DTC code P0521. The document cites another bulletin, 10-06-01-008, as a reference on how to repair and clean engines equipped with a PF48E oil filter. This solution might address the issue, according to the bulletin. The document also details other repair recommendations and instructions.

A Quick Note on Oil Pressure for Different OEMs

Some (not all) hybrid engines won’t start if the ECM doesn’t see oil pressure, so on those, the engine oil pressure sensor can cause a no-start. Keep that in mind if you have a hybrid.

But on a Chevy, for example, the ECM/PCM reads the three-wire engine oil pressure sensor, sends that information to the body control module (BCM), and the BCM passes the information along to the instrument cluster to provide the gauge with oil pressure information.

Other OEMs function in a similar fashion.

In other words, rather than the oil pressure sending unit reporting directly to the oil pressure gauge in the cluster as it was in the old days, the cluster is now a computer in its own right, and the needles are driven by stepper motors and whatnot and the signal comes to the cluster via network bus.

You won’t get this code on an older vehicle that doesn’t use the bus to report oil pressure to the cluster.

Products Mentioned in this Guide

Any information provided on this Website is for informational purposes only and is not intended to replace consultation with a professional mechanic. The accuracy and timeliness of the information may change from the time of publication.

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Todds auto repair

Tried a new pump pickup tube oil pan bypass valve new or ing behind cam retainer plastygauged rod and main bearings new valve over but all didn’t fix oil pressure hot idle 15 lbs at 1000 30 lbs hot but code p0521 still returns

Miller Melden

I need to know as well. Having the same problem in my Sierra. 5.3

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