Powertrain, generic (extended)

P23BC NOx Sensor Calibration Memory (Bank 1 Sensor 3)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Memory inside the sensor control unit corrupted or failed
Voltage dips or spikes on the sensor supply disturbing the memory
Replacement sensor with a calibration that does not match the vehicle

Symptoms

  • Check engine light on
  • Sensor 3 readings ignored by the engine module
  • SCR monitoring cannot complete

Repair estimate

DifficultyEasyDIY possible
Parts and labour€200–900
Time0.5–1.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

nox sensor b1s3

Related codes

P23ABP23C1P225AP225B

References: law.cornell.edu, gsi.ext.gm.com, fordservicecontent.com.