Powertrain, generic (extended)

P23AC NOx Sensor Circuit (Bank 1 Sensor 3)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P23AC is the general electrical fault reported for NOx sensor 3 on bank 1. The sensor's own control unit watches the leads between its electronics and the ceramic probe and tells the engine computer over CAN whether a measuring circuit is open or shorted; the user manual of Drivven's NOx sensor module kit, published by NI, lists these status states for the NOx and O2 circuits. No manufacturer documents P23AC publicly. For its front sensor, Ford's 2023 diesel summary sets P2200 when the probe lines Vs, COM, Ip1 or Ip2 short to battery or ground. CARB requires NOx sensor monitoring to catch broken circuits and readings outside the possible range. More specific sensor 3 codes run from P23AD to P23B0; P2200 and P229E are sensors 1 and 2. Without a valid signal the final SCR check stops.

Likely causes

Lead between probe and sensor control unit damaged by heat or chafing
Corroded or loose terminals at the sensor 3 connectors
Probe or sensor electronics failed internally

Symptoms

  • Check engine light on
  • No NOx reading from sensor 3 in live data
  • SCR system warning

Repair estimate

DifficultyMediumDIY possible
Parts and labour€50–900
Time0.5–2.5 h

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

Parts involved

nox sensor b1s3

Related codes

P23ADP23AEP23AFP23B0P2200P229E

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