Powertrain
generic / SAE
P24F5
NOx Sensor Delayed Response - High to Low Bank 1 Sensor 2
The post-catalyst NOx sensor on bank 1 (sensor 2) reacts too slowly when NOx in the exhaust drops from a high to a low level. Same failure mechanism as the upstream sensor — aged element, soot or condensate — but post-catalyst the consequence is a degraded SCR conversion-efficiency monitor.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number4 / F5
Possible causes
- Aged sensor element with reduced response speed high
- Soot clogging the protective tube medium
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: 300–1200 €
- Estimated time: 0.6–2 h
- Component: nox sensor b1s2
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012