Powertrain
generic / SAE
P22FD
NOx Sensor Performance Slow Response High to Low Bank 1 Sensor 2
The downstream NOx sensor on bank 1 (post-SCR) responds too slowly when NOx levels fall after a reductant injection event. The control unit measures the time between commanded reductant dose and the resulting NOx drop and finds it exceeds the diagnostic threshold, indicating an aged sensor element.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number2 / FD
Possible causes
- NOx sensor element aged or thermally damaged high
- SCR efficiency reduced (catalyst aged or contaminated) medium
- Reductant injector dosing drift low
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)
Inspection / repair
- Difficulty: medium
- DIY: shop recommended
- Estimated cost: 400–900 €
- Estimated time: 1–2 h
- Component: nox sensor post scr b1
- Component: scr catalyst
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012