OBD-II code · Powertrain (generic, extended)
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.
Is it safe to drive with P24F5?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyAged sensor element with reduced response speed
- PossibleSoot clogging the protective tube
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)
Repair at a glance
- Difficulty
- Medium
- DIY friendly
- Best left to a mechanic
- Typical labour
- 0.6–2 h
- Emissions test
- Likely to fail
- Parts involved
- Nox Sensor B1s2
Related codes
- P24F4NOx Sensor Delayed Response - High to Low Bank 1 Sensor 1
- P24F2EGR Temperature/Charge Air Cooler Temperature Correlation
- P24F3Reductant Tank Temperature/Fuel Temperature Correlation
- P24F6Exhaust Aftertreatment Fuel Air Purge Valve Stuck Open
- P24F7Exhaust Aftertreatment Fuel Air Purge Valve Stuck Closed
- P24F8Exhaust Aftertreatment Fuel Air Purge Valve Control Circuit
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.