P238BWater in Fuel Sensor B Circuit Range/Performance
- Generic OBD-II code · Powertrain
- How the car detects it
- P238B means water-in-fuel sensor B delivers a signal that is electrically valid but implausible, for instance a value stuck between the clear dry and wet states, or a self-test answer that arrives at the wrong moment. No manufacturer documents P238B publicly. On 2022 Ram heavy-duty diesels sensor B is fitted to the frame-mounted filter, exposed to road spray (Stellantis case S2214000004). The probe judges conductivity, so a film of dirt, biodiesel deposits or a partly corroded electrode can shift its reading. For the sensor A codes on 2025–26 Ram trucks Stellantis advises draining both filter stages and wiping the probe before replacing anything, a sensible first step here as well. Unlike P238F it does not confirm water.
- What you may notice
- Water-in-fuel warning without water being found
- Warning that persists after draining
- Likely causes
- LikelyDirt film or deposits on the sensor electrodes
- PossibleResidual water or emulsion around the probe after incomplete draining
- PossibleCorroded or aged sensor
- Repair
- Easy · Often possible to do yourself.Typical cost: €0 – €250
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.