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P20EE: SCR NOx catalyst efficiency below threshold (bank 1)

The SCR catalyst, which uses AdBlue to clean up nitrogen oxides, is not performing well enough. Usually poor AdBlue, the injector or a sensor.

Code P20EE at a glance
CodeP20EE
SystemEngine and transmission
GroupP20xx, Emissions: catalysts and AdBlue
TypeGeneric: it means the same on every make
Can you keep driving?With care

What P20EE means

Many modern diesels inject AdBlue (a urea solution) into the exhaust so the SCR catalyst can turn nitrogen oxides into nitrogen and water. Two NOx sensors, before and after, check that it works. The ECU sees that more NOx than allowed is left at the outlet.

Most common causes

  • Poor quality, diluted or very old AdBlue
  • AdBlue injector blocked with crystals
  • Faulty or drifting NOx sensor
  • Exhaust leak ahead of the SCR catalyst
  • Aged or damaged SCR catalyst
  • AdBlue pump or lines not reaching the correct pressure

Symptoms

  • Engine warning light on
  • AdBlue or emissions warning on the dashboard
  • Possible countdown before the engine is prevented from starting
  • Usually nothing noticeable when driving

Can you drive with P20EE?

With care You can drive, but get to a garage soon. On many cars, if the fault persists, a dashboard message counts down the distance left before the engine will not restart.

How to check it

If you topped up AdBlue recently, tell the garage where and when. On your scanner, compare the two NOx sensors: if the outlet one reads almost the same as the inlet one, the SCR is not doing its job.

How to read and clear P20EE with Final OBD

Plug an OBD2 scanner in under the steering wheel, switch the ignition on and open Final OBD. Under Faults you’ll see P20EE with this same explanation and whether it’s confirmed, pending or permanent.

With Free you read this code with its short description for nothing, and clear it if the engine stores it over standard OBD. With Pro you get the full explanation, how the car was running when it was logged (revs, temperature, load) and clearing in every control unit.

Clearing the code only turns the light off: if the cause is still there, it comes back. Clear it once it’s fixed, and not right before the ITV. It’s all in how to read and clear fault codes and in the ITV and OBD.

Similar codes

P20EE is a generic code, so it means the same on any make, for example on Abarth, Cupra, Jeep, Nissan, Seat, Škoda. See what Final OBD does on your car in makes and models.

What does code P20EE mean?

Many modern diesels inject AdBlue (a urea solution) into the exhaust so the SCR catalyst can turn nitrogen oxides into nitrogen and water. Two NOx sensors, before and after, check that it works. The ECU sees that more NOx than allowed is left at the outlet.

Can you drive with P20EE?

You can drive, but get to a garage soon. On many cars, if the fault persists, a dashboard message counts down the distance left before the engine will not restart.

How do you clear P20EE?

With an OBD2 scanner and an app like Final OBD, which clears it for free if it’s stored by the engine control unit. But clearing it only turns the light off: if the cause isn’t fixed, P20EE comes back.