P238F: Water in Fuel Condition Sensor B

What it means

The sensor reports a water-in-fuel condition. Whether water is present and how the warning is handled depend on the vehicle; follow the vehicle’s owner’s manual.

At a glance

• Usually lights the check-engine light

How it works

Water-in-fuel sensor B monitors the fuel for water, often at a filter or separator. The control module sets this code when sensor B reports a water condition; the vehicle determines how it responds to that report.

Common causes

Most likely first.

1. Water detected in the fuel filter or separator
2. Contaminated fuel
3. Water-in-fuel sensor B or wiring fault

Symptoms

• Water-in-fuel warning light on
• Check-engine light may come on
• Possible reduced engine power

How to diagnose it

1. Read freeze-frame data and check whether the water-in-fuel warning is active to confirm the conditions when the code set.
2. Check the owner’s manual for the location of sensor B and the vehicle’s procedure for checking or draining the fuel filter or separator.
3. Inspect the filter or separator for collected water and follow the manufacturer’s service procedure if water is present.
4. If the fuel appears contaminated, check the source and condition of the fuel before replacing electrical parts.
5. Inspect sensor B’s connector and wiring for moisture, corrosion, loose pins, or damage, then test the sensor circuit against the manufacturer’s specification.

Common fixes

• Drain water from the fuel filter or separator as directed by the vehicle’s service procedure.
• Replace contaminated fuel and service the fuel system as required.
• Repair damaged or corroded sensor B wiring or connector terminals.
• Replace water-in-fuel sensor B if it fails testing.

Can I keep driving?

Follow the owner’s manual promptly; water in diesel fuel can damage fuel-system components, and reduced power may make driving unsafe. Avoid hard acceleration, and stop if the engine runs poorly or loses power.