Reductant Injection Air Pressure Too Low
The DEF system air-assist pressure is below the required threshold — pump weak, line leak, or pressure-control valve stuck open.
Affected components
- Reductant air pump
- Reductant air pressure control valve
- Reductant air line
Common causes
- High likelihood: Air pump weak
- Medium likelihood: Leak in air line
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
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.