P225DNOx Sensor Performance - Signal Biased/Stuck Low (Bank 1 Sensor 1)
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Needs a drive cycle to confirm a fix
- How the car detects it
- P225D is the opposite case to P225C: the upstream NOx sensor of bank 1 reads too little NOx or refuses to rise when the engine should be producing it. Volvo and Mack list P225D among NOx codes where the sensor is very unlikely to be at fault, because the probe is simply measuring fresh air; their guide says not to replace it. FCA uses P225D on the 3.0 EcoDiesel, from 2014 Ram 1500 and Grand Cherokee flash bulletins to 2020 Ram 1500 updates, and its 2021 case file for Wrangler, Gladiator and Ram 1500 reports mostly fault-free returned sensors; it names charge air or EGR leaks, fuel contamination that soots up the sensor ports and skewed MAF or coolant inputs. A low-reading sensor hides real NOx, so SCR control and the catalyst monitor lose accuracy.
- What you may notice
- MIL on
- Code persists after a new NOx sensor
- Possible related intake, EGR or MAF codes
- Likely causes
- LikelyCharge air, intake or exhaust leak that lets the sensor see diluted gas
- PossibleSensor ports clogged with soot, for example after fuel contamination
- PossibleLow-pressure EGR valve partly stuck open
- PossibleOutdated engine control software that a published flash corrects
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €100 – €900
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.