OBD-II code · Powertrain (generic, extended)
P23B4 NOx Sensor Heater Sense Circuit Bank 1 Sensor 3
A general circuit fault on the heater sense feedback for the bank 1 sensor 3 NOx sensor - the line over which the ECU verifies that the heater is actually drawing current.
Is it safe to drive with P23B4?
Usually safe to drive in the short term. Get it diagnosed when convenient, sooner if the car drives differently.
Common causes
- Most likelyOpen in heater sense line
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
- P23B1NOx Sensor Heater Control Circuit Open Bank 1 Sensor 3
- P23B2NOx Sensor Heater Control Circuit Low Bank 1 Sensor 3
- P23B3NOx Sensor Heater Control Circuit High Bank 1 Sensor 3
- P23B5NOx Sensor Heater Sense Circuit Range or Performance Bank 1 Sensor 3
- P23B6NOx Sensor Supply Voltage Circuit Bank 1 Sensor 3
- P23B7NOx Sensor Heater Control Circuit Range or Performance Bank 1 Sensor 3
Code data: OBDex open dataset (CC0). Labour times are typical ranges, not a quote.