NOx Sensor Performance - Slow Response Low to High (Bank 1 Sensor 1)
NOx sensor on bank 1 sensor 1 responds too slowly when NOx concentration rises (typically observed when SCR dosing is reduced or stopped). The sensor has aged or its protection cap is clogged.
Affected components
- Nox sensor
Common causes
- High likelihood: Sensor aged or protection cap clogged
- Low likelihood: Sensor element aged beyond calibration window
- Low likelihood: Sensor element contaminated by oil, soot or coolant
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.