P0521 – Engine oil pressure sensor/switch -range/performance problem

By Justin DeSantis (Contact Me)
Last Updated 2016-10-30
I have over 20 years experience working on anything with an engine.

Table of Contents

1. What Does Code P0521 Mean?
2. What are the common causes of code P0521 ?
3. What are the symptoms of code P0521 ?
4. How do you troubleshoot code P0521 ?
5. Codes Related to P0521
6. Get Help with P0521

What Does Code P0521 Mean?

The oil in your vehicles engine is pressurized and pumped to all the areas where lubrication is needed. In order to monitor the oil pressure, a pressure sensor is present on all modern engines. P0521 means that the Powertrain control module or PCM has received a low pressure warning from the engine oil pressure sensor. If oil pressure drops too low or is lost all together, severe damage to the engine could result. When the P0521 fault is present, the vehicle should not be driven until the cause is found.

What are the common causes of code P0521 ?

• Low oil level
• Faulty pressure sensor
• Clogged oil passage
• Clogged oil pump pick up screen
• Wrong viscosity of oil
• Faulty oil pump

What are the symptoms of code P0521 ?

Normally, the only symptom will be the check engine light. Some models will have a separate oil pressure light that will also illuminates. Note: On some vehicles the check engine light will flash if the PCM senses conditions that could damage the engine. In some cases, a loss of oil pressure will result in noise from the valve train. Vehicles with hydraulic lifters rely on oil pressure to keep the lifters pressurized. If the check engine light is flashing, or there is any abnormal engine noise, stop driving the vehicle immediately. Severe damage can result from operating the engine with low oil pressure.

How do you troubleshoot code P0521 ?

As always, diagnosis should start with the simplest solutions first. Make sure the oil is full to the specified level, with the proper oil. If the oil is very old and dirty, it needs to be changed. Before oil pressure can be properly tested, make sure the engine is full to the specified level with the correct oil, for the operating conditions. Check the oil level. If the level is low, it should be filled with the proper oil. You will also want to consider why the oil level is low. If there is an obvious leak, it will need to be repaired. On higher mileage vehicles, it is not uncommon for worn valve seals to allow engine oil to enter the combustion chamber and be burnt. Oil level must be monitored in this situation to ensure the oil level is always maintained. If the oil loss becomes so rapid that excessive smoke is detected from the exhaust, or oil level drops too quickly, the engine should be repaired, or in some cases, it might be more feasible to replace the engine with a remanufactured unit. Once the oil level is correct, operate the vehicle and see if the code returns. If so, check the oil pressure. If possible, hook a mechanical oil pressure gauge to the engine according to the model specific service manual. Most auto parts stores will loan or rent this type of tool. If the oil pressure is within specified range, see below. If it’s not, then the lubrication system needs to be thoroughly inspected. If not blockages are found, the oil pump likely needs replaced.

If the oil pressure reads normal, and the engine has the specified amount of oil, then the fault is likely being caused by the sensor itself, or, by the associated wiring. Look at the wiring leading to the oil pressure sensor. Pay special attention to wiring that may be damaged by heat, or rub on the chassis or engine. Look for any signs of broken or damaged wiring, repair or replace as needed. If the wiring looks good, then the oil pressure sensor itself should be tested according to the service manual. If it tests out of range, replace it.

Note: On certain vehicles, especially GM models, the oil pressure sensor is a known flaw. Consult with the dealership to see if there is any service bulletins regarding the oil pressure sensor. If this is the case, the problem will usually be cured by replacing the sensor, with no further diagnosis needed.

Codes Related to P0521

• P0520- Oil pressure out of range Too high or low. Often accompanies other oil pressure codes.
• P0522- Oil pressure sensor out of range. Too low.
• P0523- Oil pressure sensor out of range. Too high.
• P0524- Oil Pressure out of range. Too low.

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