Powertrain, generic (extended)

P238B Water in Fuel Sensor B Circuit Range/Performance

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

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.

Likely causes

Dirt film or deposits on the sensor electrodes
Residual water or emulsion around the probe after incomplete draining
Corroded or aged sensor

Symptoms

  • Water-in-fuel warning without water being found
  • Warning that persists after draining

Repair estimate

DifficultyEasyDIY possible
Parts and labour€0–250
Time0.3–1.5 h

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

Parts involved

water in fuel sensor b

Related codes

P238AP238FP2265

References: static.nhtsa.gov, static.nhtsa.gov, en.wikipedia.org.