OBD-II code · Powertrain (generic, extended)
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.
Is it safe to drive with P23B2?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyHeater control line shorted to ground
- Less likelyConnector pins corroded - high contact resistance
- Less likelyHarness chafing through insulation
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
- 1–2 h
- Emissions test
- Likely to fail
- Parts involved
- Nox Sensor B1s3 Heater
Related codes
- P23AFNOx Sensor Circuit High Bank 1 Sensor 3
- P23B0NOx Sensor Circuit Intermittent Bank 1 Sensor 3
- P23B1NOx Sensor Heater Control Circuit Open Bank 1 Sensor 3
- P23B3NOx Sensor Heater Control Circuit High Bank 1 Sensor 3
- P23B4NOx Sensor Heater Sense Circuit Bank 1 Sensor 3
- P23B5NOx Sensor Heater Sense Circuit Range or Performance Bank 1 Sensor 3
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.