P225ANOx Sensor Calibration Memory (Bank 1 Sensor 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- How the car detects it
- P225A concerns the front NOx sensor of bank 1, the one ahead of the SCR catalyst. Modern NOx probes come with their own control unit that holds a sensor-specific calibration and reports finished values over CAN; this code means the stored calibration data of that unit cannot be read or fails its check. Ford's 2014 PCM code table carries P225A as a MIL code, but no manufacturer publishes the test or a threshold. Ford's 2023 diesels report memory errors inside the NOx sensor module under P2200 instead. CARB requires NOx sensor faults to be caught when the sensor can no longer serve as a feedback or monitoring input. P225B is the same fault on the downstream sensor. Usually the sensor assembly is replaced, as its memory cannot be repaired.
- What you may notice
- MIL on, usually without any change in how the engine runs
- SCR dosing runs without valid feedback, so NOx emissions may rise
- Follow-up NOx catalyst efficiency codes possible
- Likely causes
- LikelyInternal memory or checksum fault in the NOx sensor control unit
- PossibleReplacement sensor with a part number or calibration that does not suit the vehicle
- RareSupply voltage dropout or poor connector contact while the module was storing data
- RareEngine or aftertreatment control unit software that misreads the sensor data
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Medium · Usually a job for a workshop.Typical cost: €250 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.