P238C

Code

Generic P — Powertrain

Water in Fuel Sensor B Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 29 RU: 22

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Corroded, loose, or damaged connector at the water-in-fuel (WIF) sensor B
Broken or shorted wiring (short to ground) in sensor B circuit
Failed WIF sensor B (internal short or open)
Water contamination present in fuel or fuel filter/water trap
Poor ground or missing reference voltage to the sensor
Faulty ECM (rare)

Symptoms

Malfunction Indicator Lamp (MIL) or warning message illuminated
Water-in-fuel warning or service message (if equipped)
Possible reduced engine performance or limp-home mode depending on vehicle
Fuel filter/water-in-fuel lamp may be on
No obvious drivability symptoms if fault is only electrical

What to check

Read and record freeze-frame and related codes; confirm P238C is current
Visually inspect fuel filter/water trap and WIF sensor B connector for corrosion, moisture, or damage
Check for presence of water in fuel filter/water separator
Backprobe sensor connector with ignition ON (engine OFF) and observe signal voltage
Check continuity and resistance of wiring between sensor B and ECM; look for shorts to ground
Wiggle wiring harness while monitoring signal to reproduce fault

Signal parameters

Typical sensor circuit uses a 0–5 V digital/analog signal or switched ground. Exact values vary by manufacturer—consult service data
Common thresholds (generic): circuit low < 0.5 V; circuit high > 4.5 V
With no water present some sensors output a high (~5 V) or open-circuit; with water contact many sensors pull the circuit low (near 0 V)
Continuity to ground on an unpowered connector: shorted circuit will show low ohms (
Reference/feeding voltage (if present) typically ~5 V from ECM—verify presence at connector pin

Diagnostic algorithm

Retrieve DTCs and freeze-frame data. Confirm P238C presence and check for related WIF or fuel system codes.
Visually inspect fuel filter/water trap area, sensor B connector and harness for corrosion, contaminants, damage, or water intrusion. Dry and clean connectors if found wet/corroded.
With ignition ON (engine OFF) backprobe the sensor B signal pin and measure voltage. Compare to expected (see signal_params) and note if voltage is low (~0 V).
Unplug the sensor B connector and check for terminal continuity to the ECM pin and for short to ground. Repair any shorted or open wiring.
Wiggle the harness and connector while monitoring the signal to expose intermittent faults. Repair broken wires or secure harness.
If wiring checks good, bench-test or replace sensor B (or swap with sensor A if identical) to see if code follows the sensor.
Inspect and, if necessary, drain and replace fuel/water separator or primary fuel filter if water contamination is present. Replace sensor if exposed to water or visibly damaged.
After repairs clear codes and perform road/in-use test or key-cycles to confirm the fault does not return.
If fault persists after harness, sensor and fuel filter replacement, perform ECM connector checks and consider ECM diagnosis/repair at a dealer-level facility.

Likely causes

Corroded pins or water intrusion at sensor B connector causing low voltage
Wire chafed and shorted to chassis ground between sensor B and ECM
Failed sensor electronics (common on sensors exposed to fuel/water)
Clogged or saturated fuel filter/water-separator with water contacting sensor
Loose or corroded ground at fuel module assembly

Fault status

⚠️ Status

Water in Fuel Sensor B Circuit Low - Detected low voltage/grounded circuit on WIF sensor B. Check sensor, connector, wiring, fuel filter/water separator, and ECM.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours