Fault code P0521 – a step-by-step guide to diagnosing and fixing it

Error code P0521 is displayed and the check engine light is on - what does this mean?

The OBD system has detected a problem with the oil pressure sensor or its circuit. This DTC P0521 indicates that the oil pressure sensor signal is outside the expected range or does not match the actual engine conditions. This fault code may have slightly different names for different manufacturers, but always refers to the oil pressure monitoring system.

What causes can this error code have?

• Defective oil pressure sensor
• Damaged cable to the oil pressure sensor
• Corroded or loose plug connections
• Low oil level in the engine
• Contaminated or incorrect engine oil
• Defective oil pump
• Clogged oil filter
• Internal engine damage or wear
• Faulty engine control unit (ECM)

What symptoms occur in parallel with fault code P0521?

• Engine indicator light: Lights up continuously or flashes
• Oil pressure warning light: May also be activated
• Engine noises: Knocking or unusual noises at low oil pressure
• Loss of power: Reduced engine power as a protective measure
• Emergency running mode: Engine switches to safety mode
• Starting problems: Difficulty starting the engine

How to fix the problem of error code P0521?

• The repair requires a systematic diagnosis, as various components may be affected.
• Check the oil level and oil quality, change the oil if necessary and bring it to the correct level
• Remove oil pressure sensor, clean or replace completely if defective
• Check wiring and plug connections to the oil pressure sensor for damage and repair
• Change the oil filter if it is clogged or contaminated
• Test the oil pump and have it replaced if defective
• Measure the mechanical oil pressure with a pressure gauge and compare with the target values
• Check engine control unit for software errors and reprogram if necessary