WRENCHIFY
Quick decodeBack to home
All codes/P20EE

P20EE

NOx Catalyst Efficiency Below Threshold

Moderate severity

The SCR catalyst on bank 1 is no longer reducing NOx to the level the ECU expects, even with proper reductant dosing and quality. Often the result of catalyst poisoning by sulphur or hydrocarbons, thermal aging, or a leak between the upstream and downstream NOx sensors.

The SCR catalyst on bank 1 is no longer reducing NOx to the level the ECU expects, even with proper reductant dosing and quality. Often the result of catalyst poisoning by sulphur or hydrocarbons, thermal aging, or a leak between the upstream and downstream NOx sensors.

Common causes

  • SCR catalyst aged or poisoned

    One of the most commonly reported causes for this code — check this first.

    high

    Typical part cost: $440-3850

  • NOx sensor drift

    A plausible cause — test and verify before replacing parts.

    medium

    Typical part cost: $440-3850

  • See all causes + fix costs

    Create a free Wrenchify account to unlock the rest for P20EE.

    Unlock causes

    Free forever · No credit card

First things to check

  1. 1Confirm the code with a scan tool and check for additional related codes.
  2. 2Inspect the relevant sensors, wiring, and connectors for damage or corrosion.

Get the full step-by-step diagnosis

Create a free Wrenchify account to unlock the rest for P20EE.

Unlock diagnosis

Free forever · No credit card

Tools you may need

Already have a compatible scanner? Use it. If not, a Bluetooth OBD2 adapter can help you confirm engine codes and check supported live sensor data before replacing parts.

Illustration of a Bluetooth OBD2 adapter, not a product photo

Basic checks

Veepeak OBDCheck BLE

A Bluetooth LE adapter for reading standard engine codes and supported live data.

View on Amazon
Illustration of a Bluetooth OBD2 adapter, not a product photo

Regular diagnostics

vgate iCar Pro BLE 4.0

A Bluetooth LE adapter with an automatic sleep feature for routine code and sensor checks.

View on Amazon
Illustration of a Bluetooth OBD2 adapter, not a product photo

Another option

OBDLink CX

A Bluetooth LE adapter to consider when comparing supported vehicles and diagnostic apps.

View on Amazon

Illustrations shown, not product photos. Check vehicle, phone and app compatibility before buying. These adapters do not guarantee access to ABS, airbags or manufacturer-specific systems. Clearing a code does not repair the fault and can reset emissions readiness monitors.

As an Amazon Associate, Wrenchify earns from qualifying purchases. This supports the app at no extra cost to you.

Related codes

See related trouble codes

Create a free Wrenchify account to unlock the rest for P20EE.

Unlock related codes

Free forever · No credit card

Frequently asked questions

What does P20EE mean?

P20EE means "NOx Catalyst Efficiency Below Threshold (Bank 1)". It is a generic OBD-II code that points to a fault in the emissions: nox, particulate, dpf, scr.

What are the most common causes of P20EE?

scr catalyst aged or poisoned; nox sensor drift; exhaust leak between upstream and downstream nox sensors — these are the most commonly reported causes. Verify with a proper diagnosis before replacing parts, or use the Wrenchify app for a vehicle-specific diagnosis.

Can I keep driving with this code?

The vehicle is usually drivable for short distances, but the problem can worsen or affect emissions. Diagnose and repair as soon as practical. Use the Wrenchify app for a full diagnosis specific to your vehicle.

Get the full P20EE diagnosis for your vehicle

Year, make, model + step-by-step repair help — free plan included.

Diagnose P20EE