Powertrain, generic (extended)

P238C Water in Fuel Sensor B Circuit Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P238C is set when the signal line of water-in-fuel sensor B stays below its valid range. Because the sensor reads conductivity, anything that bridges its terminals or pulls the signal to ground can cause it: a chafed wire, a wet connector or a sensor body full of water. No manufacturer documents P238C publicly. For the matching sensor A code P2266 Ford bulletin 18-2133 on 2017–18 Super Duty 6.7L trucks traced the fault to water in connector C3080 and specified a sensor resistance of 795 to 815 kOhm across pins 1 and 2; on Ram trucks sensor B is the one in the chassis filter. Since a wet plug may imitate both a low circuit and real water, check for P238F as well. The opposite fault is P238D.

Likely causes

Water bridging the terminals in the sensor connector
Signal wire chafed through to ground on the frame
Sensor resistance out of specification

Symptoms

  • Water-in-fuel lamp on
  • Fault appears after washing or rain

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

P238DP238AP238FP2266

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