Powertrain, generic (extended)

P225B NOx Sensor Calibration Memory (Bank 1 Sensor 2)

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P225B is stored when the control unit of the downstream NOx sensor on bank 1 cannot provide valid calibration data from its memory. That sensor sits behind the SCR catalyst and is what the engine computer uses to judge how well urea dosing reduces NOx, so a sensor without trustworthy calibration leaves the catalyst monitor blind. Ford lists P225B as a MIL code in its 2014 PCM code table; a description of the check is not public from any manufacturer. Smart NOx sensors of the Continental type keep an OEM-specific calibration in their attached module, which is why a part for another vehicle can trip such a code. P225A is the upstream counterpart, while P229E to P22A1 cover the electrical faults of this downstream sensor.

Likely causes

Corrupted or unreadable calibration memory in the downstream NOx sensor module
Sensor installed with the wrong part number or an OEM calibration for another application
Moisture or corrosion at the sensor module connector disturbing its supply

Symptoms

  • MIL on with no driveability complaint
  • SCR efficiency monitor does not complete or reports P20EE
  • Possible emissions test failure because readiness stays incomplete

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€250–900
Time0.5–2 h

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

Parts involved

nox sensor

Related codes

P225AP229EP22A1P20EE

References: law.cornell.edu, performanceparts.ford.com, ni.com.