Powertrain, generic (extended)

P238A Water in Fuel Sensor B Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P238A is the general circuit code for water-in-fuel sensor B, used where a diesel has two water-detecting points, for example a frame-mounted primary filter and a second separator. Stellantis case file S2214000004 for 2022 Ram 2500 to 5500 trucks shows that on these vehicles the B sensor is part of the fuel filter mounted on the frame; P238A itself is not named there. No manufacturer documents P238A publicly. The sensor works like sensor A: two electrodes in the water sump read the conductivity. GM's 2018 diesel tables describe a self-test for sensor A in which a healthy probe briefly reports water right after power-up; a missing pulse counts as a circuit fault. While the code is stored, real water in the filter may go unnoticed, so drain the separator regularly.

Likely causes

Water or corrosion in the sensor B connector at the chassis filter
Damaged harness along the frame rail
Water-in-fuel sensor B failed

Symptoms

  • Water-in-fuel lamp or message on
  • No warning for real water in the chassis filter

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 bfuel filter housing b

Related codes

P238BP238CP238DP238EP238FP2264

References: static.nhtsa.gov, gsi.ext.gm.com, en.wikipedia.org.