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EmissionsSeverity Medium: diagnose soon

P20EESCR NOx Catalyst Efficiency Below Threshold (Bank 1)

What it means

The NOx sensors show that the SCR catalyst isn't reducing NOx as much as it should.

Symptoms

  • AdBlue or emissions warning
  • Countdown to a no-restart condition on many cars
  • Usually no change in power until the countdown ends

Common causes

  • Poor quality or diluted AdBlue
  • Under-dosing: blocked dosing valve or low pressure
  • Faulty NOx sensor
  • Aged or contaminated SCR catalyst

What to check first

  1. Check AdBlue quality with a refractometer (about 32.5 % urea)
  2. Run a dosing quantity test
  3. Compare upstream and downstream NOx readings
Can I drive with P20EE? Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.

Generic OBD-II meaning. Manufacturer-specific meanings and checks can differ; always check the service information for the car.

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P20EE: questions and answers

What does P20EE mean?

P20EE: SCR NOx Catalyst Efficiency Below Threshold (Bank 1). The NOx sensors show that the SCR catalyst isn't reducing NOx as much as it should.

What are the symptoms of P20EE?

AdBlue or emissions warning. Countdown to a no-restart condition on many cars. Usually no change in power until the countdown ends.

What causes P20EE?

Poor quality or diluted AdBlue. Under-dosing: blocked dosing valve or low pressure. Faulty NOx sensor. Aged or contaminated SCR catalyst.

How do you diagnose P20EE?

1. Check AdBlue quality with a refractometer (about 32.5 % urea) 2. Run a dosing quantity test 3. Compare upstream and downstream NOx readings

Can I drive with P20EE?

Usually yes for a short distance, but performance or economy may suffer and the fault can get worse. Diagnose it soon.