Reductant Injection Air Pressure Too High
The DEF system air-assist pressure exceeds the upper threshold — pressure-control valve stuck closed or air pump runaway.
Affected components
- Reductant air pump
- Reductant air pressure control valve
Common causes
- High likelihood: Pressure control valve stuck closed
- Medium likelihood: Air pump does not regulate
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
Related codes
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.