NOx Exceedence - Insufficient Reagent Quality
The diesel exhaust aftertreatment system detects elevated NOx levels combined with abnormal reagent (AdBlue/DEF) consumption, indicating that the reagent quality is insufficient or contaminated. Many regions trigger driver inducement (limited restarts).
Affected components
- Scr catalyst
- Def tank
- Nox sensor
- Def quality sensor
Common causes
- High likelihood: Non-DEF liquid in tank (water, diesel)
- Medium likelihood: Aged or diluted DEF/AdBlue
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.