P20EE on Dacia: How to Diagnose & Fix

P20EE stands for "SCR NOx Catalyst Efficiency Below Threshold." This is a diesel emissions code meaning the Selective Catalytic Reduction (SCR) catalyst on Bank 1 is not cleaning up exhaust as well as it should. The SCR system sprays Diesel Exhaust Fluid (DEF) into the hot exhaust to convert harmful nitrogen oxides (NOx) into harmless nitrogen and water; NOx sensors before and after the catalyst tell the computer how well it is working. When the measured efficiency falls below the required threshold, this code sets. Because it is an emissions-protection code, it often triggers warning lights and can lead to reduced power or a speed limit (a 'derate') if left unfixed. On Dacia it is documented across 1 model: Duster.

The most common causes of P20EE are: Poor quality, contaminated, or wrong DEF fluid, Faulty or clogged DEF injector/dosing valve, Failed upstream or downstream NOx sensor, Degraded or failed SCR catalyst, Exhaust gas temperature sensor fault affecting dosing, Exhaust or DEF line leak, DEF line/heater problems (crystallization or freezing). The specific cause varies by vehicle.

Published repair estimates on Dacia range from $300 to $1,500 depending on the model and root cause. If an issue mentions a recall or campaign, check your VIN with the manufacturer or NHTSA and confirm eligibility and coverage with a dealer.