1. Home
  2. /
  3. Complete List of OBD2...
  4. /
  5. P0521 Code – What...

P0521 Code – What Does this Mean & How to Fix

This is one of the most frequent OBD2 trouble codes. Read the full article below to know what it means, how to fix it, and what other codes may show related to it.


Engine Oil Pressure Sensor/Switch Range/Performance


The fault code P0521 shows up when the car’s main computer, also referred to as the Power control module, monitors and records atypical activity in the engine’s oil pressure. This variation or abnormality in the readings on the ECM can be in both directions; meaning that it is not mandatory that the abnormality is always in the form of an excess in engine oil pressure. The P0521 error can also arise in case the engine oil pressure observed is below the normal range. Hence, the abnormality in the oil pressure can be of both natures- excess or scarcity of oil pressure in the engine. 

The PCM (power control module) controls multiple sensors present in the engine. It is also responsible for controlling the Oil Pressure Sensor. The oil pressure sensor monitors the levels of engine oil pressure and transmits this information to the PCM in the form of voltage values. The PCM in turn detects any abnormalities recorded in these voltage values and informs the driver. Fault code P0521 can also surface if oil pressure is stagnant when a significant range of activity is expected.

When P0521 eventuates in the engine, the PCM transmits this information to the driver in the form of lighting up of the malfunction indicator lamp on the dashboard. The Malfunction Indicator Lamp, also often referred to as the ‘check engine light’, is the tell-tale that there is a malfunction in the engine which needs to be addressed.


The fault error P0521 can be caused due to multiple reasons. Some of the prominent causes of the P0521 error are stated below:

  • Low levels of oil present in the car’s engine
  • Dirty oil in the engine due to delayed oil change
  • Low oil pressure
  • Low quality oil
  • Fault in the oil pressure sensor
  • Wiring or circuit fault in the oil pressure sensor
  • Mechanical engine failure
  • Leakage in the engine’s oil duct


In addition to the lighting up of the Malfunction illumination lamp, the following symptoms can be experienced by the driver when the P0521 fault code is present in the car’s engine:

  • The oil pressure gauge shows a low or a high level of oil pressure
  • Loud noises coming from the engine


Steps for Self-diagnosis:

A lightened up Malfunction lamp in your dashboard is your cue to check your vehicle’s oil pressure levels. As a car owner, the first step towards diagnosis is for you to check the oil levels yourself with the help of the dipstick.

– You should then look for any leakages in the oil filter or in the oil duct. 

-You can then check if the type of oil used is the one suitable for your car’s engine as fault codes can be experienced due to the wrong type of oil being used.

-You can then look for any burnt spots or broken wires in the engine’s circuit. At this point you would want to be careful while examining the engine and try to limit your inspection to visual examination only. 

Steps for professional diagnosis:

The mechanic will first extract all the fault codes from the power control module’s memory using the OBD 2 scanner. He would then use one-of-two methods to rule out or fix the P0521 engine fault code.

-Manually check the oil pressure in the engine using the mechanical oil pressure tester which is installed in the engine. Then the mechanic will compare these statistics with the readings from the PCM. In case the oil levels are lower than the desired level, the mechanic will restore the oil level. In case there is any imparity in the two readings, then this may suggest that the oil pressure sensors may need a repair or a replacement.

– The second method that the mechanic can use to check the accuracy of the readings provided by the PCM is by using a digital volt ohm meter (DVOM) to check the sensor and the current flow in the circuit. There are manufacturer’s set criteria for the level of current that is required to flow in the circuit of the oil pressure meter. In case the reading on DVOM does not coincide with the criteria, the oil pressure sensor may need a replacement. 

The mechanic may also need to check the wires and connectors for possible breakage or burns as these may result in the oil pressure sensor generating faulty readings, hence, resulting in P0521 error.

Common mistakes in diagnosis:

The mechanic may simply end up replacing the oil pressure sensor. This will result in the clearing of fault codes from the PCMs memory and the disappearance of the Malfunction icon from the dashboard. However, there is a possibility that the engine has been damaged due to the earlier presence of P0521 which may go unnoticed.

How serious is the DTC P0521 error code?

If not fixed and left unattended for a prolonged period of time, the P0521 fault code can result in the complete failure of the engine.

How to fix this?

The P0521 is an error which can be avoided if timely oil change exercises are carried out along with resetting of the oil pressure sensors. It is also imperative to make sure that the electrical connectors are in place and corrosion free.

Related codes

Other codes related to P0521 are:

P0522, P0523, P0524 and P0520.


With sufficient oil changes and regular maintenance, it is possible to avoid the P0521 error code from occurring.  Although P0521 can pose a serious challenge, a timely visit to the mechanic and efficient diagnosis can help eliminate the P0521 error without causing any significant damage to the engine.

P0521 Code – What Does this Mean & How to Fix