Ford F150 P0521: Oil Pressure Sensor Switch → Performance/Range

P0521 An OBD2 diagnostic code is generated when the vehicle is detected as having an OBD2 fault. Ford F150 The oil pressure sensor detects an error and sends a message to inform the user that it is outside its normal operating range.

This is usually caused by an oil pressure sensor problem or an oil system issue. It should be immediately diagnosed and repaired.  It is possible, and even probable that an oil pressure sensor/sensor is defective. However, it could also indicate a problem in the oil pressure.  

Your F150’s oil pressure sensor measures the oil pressure mechanically, and converts that reading into a voltage signal that the PCM (Powertrain Control Module) converts into an oil pressure reading.  This is the reading that you will see on your oil gauge. It also triggers an oil warning light.

P0521 Quick facts

• Most often caused by an issue with your F150’s oil pressure sensor or circuit
• You should take P0521 very seriously
• A common sign is an oil light, or an inaccurate reading on the oil pressure gauge.
• Simple to diagnose

P0521 Symptoms:  Ford F150

These are some of the symptoms that P0521 is most commonly associated with:

• Glow-low Oil Light/Gauge Although P0521 can often be caused by an oil pressure sensor problem, it is important to treat readings from your oil gauge or low oil warning as if they were correct.
• Ticking, Knocking, and Other Things If your engine is ticking and knocking, it’s likely that the oil pressure sensor is accurate and there’s a problem with the engine or you need oil.
• Check Engine Light– That’s why you are here.

F150 P0521 Causes

The problem with your sensor wire or sensor sensor is what causes P0521. This would indicate that your engine is in good condition.  Or it is going to be caused by an issue your F150’s oil level, viscosity, pressure, or cleanliness.  

Proper oil flow is vital to an engine's performance. This code must be respected and followed.

These are some of the leading causes for P0521.

• You can have low or no oil The first thing that you should do is check to see if there is oil in your F150’s engine at all.  It can also throw the P0521 error if it is very low or empty.  Clear the code and fill up the oil.  
• Low Oil Pressure This code may appear if the oil pressure is too low.  This code should be accompanied by the oil light or low oil pressure readings from the oil gauge.  Ford F150 Low oil pressure diagnosis
• Wrong oil or dirt? If there hasn’t been an oil change for a long enough period of time, it can interfere with the oil pressure sensor, even if there still is oil pressure. 
• Oil Pressure Sensor Wiring - P0521 means that the oil pressure sensor signal is not in range.  This is a signal that there are wiring problems.
• Oil Pressure Sensor It is possible that the problem may be caused by an oil pressure sensor. However, the smart thing to do is check the wiring and the oil.

P0521 Diagnostics F150

This P0521 diagnosis order is written (like everything on the site) for the DIY guy who doesn’t have a lot of specialty tools. 

1. Take a look at the oil

Check the oil level first.  If it’s full make sure that it looks healthy.  You may have an oil pressure sensor problem if the lid appears blackened or grimy.

2. Check the Wiring Harness

Next, you should inspect the wiring harness running from the oil pressure sensor to the PCM.  It could also be the cause of P0521.  Don’t forget to make sure that the harness is still plugged into the sending unit and undamaged.  

This code can be thrown for many reasons, including wiring issues.  The wiring is close to the F150’s exhaust and can get brittle over time.

3. Manually check your oil pressure

After confirming that both the wire and the oil level are good, it is time to check the oil pressure manually.  A Manual oil pressure gauge to see if it’s where it needs to be.  They're easy to use.  Here’s a Great YouTube Video That will explain exactly how to use this gauge for checking.

If the oil pressure from the gauge reads ok, you’ll need to replace the oil pressure sending unit/sensor.  They’re cheap.  If there is low or no oil pressure, you’ll need to figure out why.

Conclusion

It’s relatively straightforward diagnosing P0521.  This is made easier by knowing the exact oil pressure.  If you have any suggestions, please leave them below. Good luck with your Ford F150.