NOx Exceedence — Insufficient Reagent
The SCR system has detected that NOx emissions exceed the legal limit and the cause is traced to insufficient AdBlue/DEF dosing. Modern emission regulations require this fault to be reported separately so that operator-induced misuse (running an empty tank, diluting the fluid) is recorded.
Affected components
- Reductant dosing unit
- Reductant tank
- Scr catalyst
Common causes
- High likelihood: DEF tank repeatedly run empty
- Medium likelihood: Diluted or contaminated DEF
- Medium likelihood: Dosing pump output below spec
Possible symptoms
- Check engine light or NOx warning on
- AdBlue/DEF level or quality warning
- Possible no-start countdown after ignore period
- Failed emissions inspection (NOx)
Diagnostic notes
- The malfunction indicator lamp may illuminate
- This code can affect emissions
- A drive cycle may be required after repair
- Reduced-power or limp mode may occur
Sources
Diagnostic information is provided for reference only. Confirm the code with a compatible scan tool and follow the vehicle manufacturer's service procedures before replacing components.