P238F

Code

Generic P — Powertrain

Water in Fuel Condition - Sensor B

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 82 RU: 21

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Water or contamination present in fuel or fuel/water separator
Saturated or damaged fuel/water filter or separator
Failed or intermittent WIF Sensor B (internal short or open)
Corroded, loose or damaged sensor connector or wiring harness
Poor ground at sensor or ECU
Aftermarket or incorrect fuel filter/part fitted

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Fuel system warning or WIF indicator (if equipped)
Rough idle, hesitation, hard start or stalling if contamination severe
Reduced engine power or derate in some systems
Visible water or milky fuel in separator/drain
Fuel smell or fuel leakage when draining separator (rare)

What to check

Retrieve freeze frame and live data for Sensor B with a scan tool
Visually inspect fuel/water separator and drain the bowl; check for water/hazardous contamination
Inspect sensor B connector and harness for corrosion, damage, or loose pins
Backprobe sensor connector and measure voltage and/or resistance with KEY ON ENGINE OFF (consult vehicle spec)
Perform a wiggle test on wiring while observing live data for intermittent changes
Check ground continuity from sensor to chassis/ECM ground

Signal parameters

WIF sensors are commonly resistive or capacitive; manufacturers differ—consult service manual for exact values
Typical resistive-type behavior (example only): dry > ~10 kΩ, wet < ~1 kΩ (specs vary)
Typical voltage-type behavior (example only): sensor output may change between low and high states (e.g., near 0–1 V vs 2–5 V); threshold often around 1–2 V
Expected behavior: stable reading with dry fuel; significant change in resistance/voltage when water contacts sensor
If reading is open circuit (infinite resistance) or short (near 0 Ω) it indicates a sensor or wiring fault

Diagnostic algorithm

Read and record freeze frame and any related codes. Note vehicle conditions when code set.
Visually inspect fuel/water separator and drain sediment/water into a clear container; check for presence of water or contaminants.
If water present, drain separator fully, replace fuel filter element per manufacturer interval, then clear codes and retest.
If no water visible or code persists after draining, inspect sensor B connector and wiring for corrosion, pin damage, loose terminals, and secure fit.
With key ON engine OFF, backprobe sensor connector and measure resistance or voltage. Compare to manufacturer specification or to expected dry/wet behavior (see signal_params).
Wiggle wiring and connectors while monitoring live data to find intermittent opens/shorts.
Check ground and supply circuit continuity from sensor to ECM; repair any opens, shorts, or poor grounds.
If wiring and power/ground are good but sensor reading is out of spec, replace WIF Sensor B and retest.
After repair, clear codes and perform a road test under conditions similar to freeze frame; re-scan to verify code does not return.
If code persists after sensor/wiring replacement, consult manufacturer service information for ECM/PCM tests and possible software updates or ECM replacement.

Likely causes

Fuel/water separator contains water above the sensor activation level
Sensor B element has failed (shorted or open circuit)
Connector pins corroded or terminals pushed out
Chafed wiring causing intermittent short to ground or battery
Recent refueling with contaminated diesel or gasoline (depending on vehicle)
Filter drain not serviced allowing accumulation of water

Fault status

⚠️ Status

P238F — Water In Fuel Condition Detected (Sensor B). Malfunction Indicator Lamp (MIL) may be illuminated; fuel system may employ protective strategies until condition is resolved.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5 - 2.5 hours