Fiat Fremont P0521: Oil Pressure Sensor Switch → Performance/Range

P0521 An OBD2 diagnostic code is generated when the vehicle is detected as having an OBD2. Fiat Fremont detects that oil pressure sensor value is not within its normal range.

This problem is often caused by a defective oil pressure sensor, or an issue in the oil system. These problems should be addressed immediately.  Although it's possible and likely that your oil pressure sender/sensor may be defective, it is also possible to have an issue with the oil.  

Your Fremont’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 Fremont oil pressure gauge. It also triggers an oil warning light.

P0521 Quick Facts

• Most often caused by an issue with your Fremont’s oil pressure sensor or circuit
• Take P0521 seriously
• Most common symptoms are the oil light and an incorrect oil pressure gauge reading.
• Simple to diagnose

P0521 Symptoms:  Fiat Fremont

Below are the top symptoms of P0521.

• Glow-low Oil Light/Gauge The most common cause of P0521 is a poor oil pressure sensor. However, the readings from an oil pressure gauge or low-oil warning should be treated as correct until you are certain.
• Ticking or Knocking - 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.

Fremont P0521 Reasons

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 Fremont’s oil level, viscosity, pressure, or cleanliness.  

This code is important because it ensures proper oil flow.

These are some of the leading causes for P0521.

• You have the option to use low- or none of your oil. The first thing that you should do is check to see if there is oil in your Fremont’s engine at all.  It can also throw P0521 if the crankcase has run out of oil or is very low in oil.  This can be fixed by filling the oil with more, clearing the code and resetting the crankcase.  
• Oil pressure is low The code will appear if oil pressure drops too low.  The code will be displayed with either the oil light on the engine or the low reading of the oil pressure gauge.  Fiat Fremont Low-Oil Pressure Diagnosis
• Wrong or dirty oil- 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 The signal from an oil pressure sensor has gone out of range. P0521 is the result.  It indicates that the wiring is not working properly.
• Oil Pressure Sensor It is possible that the problem may be caused by an oil pressure sensor. However, it's smart to first look at the oil and wiring.

P0521 Fiat Fremont Diagnosis

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. Examine the oil

First, check your oil level.  If it’s full make sure that it looks healthy.  You may have an oil pressure sensor problem if the lid appears black or grimy.

2. Examine the Wiring Harness

Next, you should inspect the wiring harness running from the oil pressure sensor to the PCM.  You could have P0521 if the wiring is damaged.  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 Fremont’s exhaust and can get brittle over time.

3. You can manually check the oil pressure

If the wiring and oil levels are in good condition, you can manually test the oil pressure.  There are two options: Manual oil pressure gauge to see if it’s where it needs to be.  They're easy to use.  Here’s a Amazing YouTube video This will demonstrate how you can use the gauge to test.

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 Fiat Fremont.