Powertrain
generic / SAE
P23B2
NOx Sensor Heater Control Circuit Low Bank 1 Sensor 3
Same as P23B1 with the heater control line shorted to ground. The sensor heater warms the element to operating temperature (~600 °C); without it the lambda sensor stays inactive in closed loop and the ECM cannot trim mixture.
SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number3 / B2
Possible causes
- Heater control line shorted to ground high
- Connector pins corroded - high contact resistance low
- Harness chafing through insulation 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: 400–850 €
- Estimated time: 1–2 h
- Component: nox sensor b1s3 heater
- MIL / check engine light
- emissions-relevant
Sources
References
sae:J2012