P225B: Ford NOx sensor 2 calibration-memory integrity fault

P225B identifies a calibration-memory CRC failure in Ford's bank 1 sensor 2 NOx controller. The code concerns whether stored calibration information passes an integrity check. It is not a report that the downstream NOx concentration is necessarily too high.

Why the sensor position matters

The 2015 summary describes sensor 2 as a tailpipe sensor typically downstream of the SCR and DPF. Its measurements can inform aftertreatment diagnosis, but unreliable calibration data must be addressed before those measurements can support a confident catalyst judgment.

Ford lists a five-second malfunction-registration period and continuous execution. The related P06EB processor-performance code encompasses a wider set of internal checks; P225B selects the calibration-memory check specifically. P225A is the corresponding memory code for sensor 1.

A bounded repair decision

Confirm the sensor identity and preserve accompanying controller and communication faults. The monitor summary does not establish that a reflash will repair the issue, or that a catalyst replacement is needed. The applicable service procedure must determine how the controller's integrity failure is diagnosed and corrected. After repair, verification should establish that the memory fault no longer occurs and that the relevant NOx measurement system is operating properly.

Source and applicability

Ford 2015 model-year diesel OBD system operation summary, revision December 22, 2014; the cited monitor only, without blanket model or engine applicability. Ford source, physical PDF pages 42, 49. The documented monitor explains the fault decision; vehicle-specific service information is still needed for connector identification and a complete repair procedure.