P20E8 – Pressure Reducer Pressure Too Low

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What does the P20E8 code mean?

The P20E8 code indicates a problem in the system that reduces pollution in diesel engines. This system, called SCR (or DEF/AdBlue), uses a special fluid to reduce harmful emissions.
This error message appears when the reducer fluid pressure is too low, which prevents the system from functioning properly.


Possible symptoms:

  • The engine warning light illuminates on the dashboard

  • Possible warning messages related to emissions or AdBlue may appear


Common causes of the problem:

  • DEF pump faulty

  • Reducer fluid injector damaged

  • Purge valve of the system no longer working correctly

  • Hose or pipe of the reducer fluid punctured or clogged

  • Pressure sensor faulty


How to resolve the problem?

  1. Visually inspect the cables and connectors related to the DEF system: look for cut wires, broken pins, or signs of corrosion.

  2. Check the main components of the system: pump, injector, sensor, valve, and pipes.

  3. If in doubt, a diagnosis with an OBD tool can help you precisely locate the fault.


🔧 Tip: This type of problem can prevent the proper functioning of the anti-pollution system and, eventually, limit the vehicle’s performance or prevent it from starting. Therefore, it is recommended to have the vehicle checked by a professional quickly.

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