P23BCNOx Sensor Calibration Memory (Bank 1 Sensor 3)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- Every smart NOx sensor carries its own control unit with a memory holding trim and reference data written for that individual probe at the factory. P23BC means this memory in sensor 3 on bank 1 cannot be read or fails its integrity check, so the engine module can no longer trust the readings. No manufacturer documents P23BC publicly. GM's 2025 table hints at what is stored there: for its sensing-element test P23C1, a reference value measured on the new sensor at the supplier plant sits in the sensor EEPROM. Ford's 2023 diesel summary files RAM, ROM and EEPROM checksum errors of the front sensor controller under P2200 instead. CARB treats NOx sensor faults as emission-relevant. P225A and P225B are sensors 1 and 2; a corrupt memory cannot be repaired.
- What you may notice
- Check engine light on
- Sensor 3 readings ignored by the engine module
- SCR monitoring cannot complete
- Likely causes
- LikelyMemory inside the sensor control unit corrupted or failed
- PossibleVoltage dips or spikes on the sensor supply disturbing the memory
- RareReplacement sensor with a calibration that does not match the vehicle
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Easy · Often possible to do yourself.Typical cost: €200 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.