P20EE on Audi
SCR NOx Catalyst Efficiency Below Threshold
P20EE on Audi vehicles indicates scr nox catalyst efficiency below threshold. Au7o has documented this code across 1 Audi model — most commonly on Q7. 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.
Common Causes of P20EE
- •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)
P20EE on Audi by Model
Audi Q7(1 issue)
- TDI Diesel Emissions Scandal and Recalls (Dieselgate)2009-2016
The 2009-2016 Audi Q7 3.0L TDI diesel was part of Volkswagen Group's emissions cheating scandal. EPA found VW/Audi failed to comply with Clean Air Act regulations - vehicles emitted up to 40x legal NOx emissions. Audi issued emissions recalls for 2009-2012 Q7 TDI (Gen 1 fix) and 2013-2016 Q7 TDI (Gen 2 fix). Some owners report reduced performance, increased DEF consumption, and DPF issues after emissions fix. Class action settlements provided compensation to affected owners.
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View P20EE across all makes →Frequently Asked Questions
What does P20EE mean on Audi?▼
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 Audi specifically, this code is documented across 1 model.
What causes P20EE on Audi vehicles?▼
Common causes on Audi: 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. Specific causes vary by model and year — see the per-model sections below.
How much does it cost to fix P20EE on a Audi?▼
Repair costs vary widely depending on the root cause and specific Audi model.
Which Audi models have P20EE documented?▼
Au7o has documented P20EE on 1 Audi model: Q7.