OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

P238A

Water in Fuel Sensor B Circuit

A general circuit fault on the secondary water-in-fuel sensor B - typically used on diesel systems with two filter housings (pre-pump and post-pump). The ECU loses water-detection feedback on this stage; risk of water reaching the high-pressure pump and injectors.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number3 / 8A

Possible causes

  • Open in sensor or wiring high

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 80–280 €
  • Estimated time: 0.4–1.4 h
  • Component: water in fuel sensor b
  • Component: fuel filter housing b
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication