Diagnostic Trouble Code
P20EE — SCR NOx Catalyst Efficiency Below Threshold — Bank 1
SCR NOx Catalyst Efficiency Below Threshold — Bank 1
Definition
The ECM has detected that the selective catalytic reduction (SCR) system is not converting NOx emissions efficiently enough. The SCR uses diesel exhaust fluid (DEF/AdBlue) to neutralize nitrogen oxides in the exhaust.
Common Causes
- Depleted or contaminated DEF fluid
- Failed DEF injector or dosing system
- Deteriorated SCR catalyst substrate
- NOx sensor malfunction giving false readings
- DEF quality sensor detecting diluted fluid