Powertrain, generic (extended)

P23AB NOx Sensor Processor Performance (Bank 1 Sensor 3)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

A NOx sensor is a smart part: the probe in the exhaust is wired to a small control unit with its own processor, which runs the heater, evaluates the cell currents and reports over CAN. P23AB means that this electronics in sensor 3 of bank 1 – usually the one behind a second SCR catalyst – reports an internal error or fails its self-checks. No manufacturer documents P23AB publicly. Ford's 2023 diesel OBD summary shows what such checks contain for its front sensor: RAM failure and ROM or EEPROM checksum errors, reported there under P2200. CARB requires NOx sensors to be monitored for faults that make them unusable for the SCR checks. P06EA and P06EB are the processor codes of sensors 1 and 2. Repair normally means a new sensor.

Likely causes

Internal electronics of the sensor 3 control unit defective
Supply voltage dips or poor ground resetting the sensor electronics
Sensor control unit damaged by heat or water ingress

Symptoms

  • Check engine light on
  • Sensor 3 values missing or frozen in live data
  • SCR or emissions warning on the display

Repair estimate

DifficultyMediumDIY possible
Parts and labour€200–900
Time0.5–2 h

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

Parts involved

nox sensor b1s3

Related codes

P06EAP06EBP23ACP23B6

References: law.cornell.edu, fordservicecontent.com, ni.com.