P20EENOx Catalyst Efficiency Below Threshold (Bank 1)
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.
Can I keep driving? With caution
You can drive to the shop, but do not postpone the repair. The problem may worsen and damage other components.
Sistema Afectado
Motor · Powertrain
La falla pertenece al grupo motopropulsor (motor y gestión electrónica).
Espacio para vendedores de repuestos
Aún no hay un anunciante en este espacio.
Symptoms You Will Notice
What you may observe when this code appears
- Check engine light on Failed emissions inspection Possibly slightly increased fuel consumption Sulfur (rotten egg) smell from exhaust under load
Possible Causes
The components or conditions that trigger this code
- 1SCR catalyst aged or poisoned NOx sensor drift Exhaust leak between upstream and downstream NOx sensors
How to Fix It — Step by Step
Recommended diagnostic and repair procedure
- 1Difficulty: hard. Estimated time: 1.5-6 hours. Estimated cost: €400-€
- 2Professional repair recommended
Note: This information is for general reference. For precise diagnostics and safety repairs, always consult a certified mechanic.
Estimated Cost
Approximate range in USD (varies by region and shop)
Varies by diagnosis
* Diagnosis only: $50–$150
Quick Info
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