Reductant System Performance (Bank 2)
The DEF system as a whole on bank 2 is not delivering the required NOx reduction — NOx-out remains too high relative to commanded dosing across a drive cycle. Causes range from poor DEF quality, restricted dosing line, weak pump, to a degraded SCR catalyst.
Affected components
- Scr catalyst
- Reductant metering unit
- Reductant quality sensor
- Reductant pump
Common causes
- High likelihood: Poor DEF quality — diluted or contaminated
- Medium likelihood: SCR catalyst thermally aged
- Medium likelihood: Crystallisation restricts dosing 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
- 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.