P23BF
NOx Sensor Performance Slow Response Low to High Bank 1 Sensor 3
NOx Sensor Performance Slow Response Low to High Bank 1 Sensor 3: the component is electrically intact but its response does not match the command.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: 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)
Common causes
Ordered by how often each turns out to be the cause.
- Sensor element agedCommon
- Sensor element contaminated by oil, soot or coolantLess likely
- 5V/reference voltage unstable under loadLess likely
Parts involved
- NOX Sensor B1s3
P23BF is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.