P23B5
NOx Sensor Heater Sense Circuit Range or Performance Bank 1 Sensor 3
Same as P23B4 with the sense voltage in plausible range yet not matching the heater model.
- 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.
- Heater current driftedCommon
Parts involved
- NOX Sensor B1s3 Heater
P23B5 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.