KlaroFault codeP20EE
MODERATESCR NOx Catalyst Efficiency Below Threshold (Bank 1)
What this code means
SCR NOx Catalyst Efficiency Below Threshold (Bank 1).
“Bank 1” is the side of the engine that holds cylinder number 1; “Bank 2” only exists on V and flat engines. An in-line engine has a single bank.
P20EE is a generic code: it means the same thing on every make. P20EE belongs to family P20xx — Fuel, air and emission controls. Its page explains how to read a code and groups all its codes by part.
AdBlue / SCR system
On recent diesels, the SCR system injects AdBlue, a urea solution, into the exhaust upstream of a dedicated catalytic converter, which turns nitrogen oxides into nitrogen and water. A pump, a heated tank, a level sensor and an injector make up the system, and NOx sensors check its efficiency.
What you notice
An AdBlue warning with a countdown of the kilometres left: once it reaches zero, the engine may refuse to restart. Some models also reduce power.
How to check it
Check the AdBlue level and quality first: old, diluted or contaminated fluid (water, diesel) is a frequent cause. AdBlue crystallises, so look for white deposits around the injector and the pipes. Then the tank heater and pump, and the NOx sensors. Always fill up with AdBlue that meets the ISO 22241 standard.
What to do
Have it checked this week. The car remains usable, but the fault will not clear itself and will fail the roadworthiness test.
Clearing a code switches the light off but repairs nothing: if the fault remains, the code comes back. Clearing a fault code yourself →
How to read this code
- PPowertrain
- 2standardised code
- 0Fuel, air and emission controls
- EEP20EE
Other codes for the same part
- P203BReductant Level Sensor Circuit Range/Performance
- P203FReductant Level Too Low
- P2047Reductant Injector Circuit/Open (Bank 1 Unit 1)
- P204FReductant System Performance (Bank 1)
- P20E8Reductant Pressure Too Low
- P20E9Reductant Pressure Too High
- P20EFSCR NOx Catalyst Efficiency Below Threshold (Bank 2)
