What it means
Same as P238A with intermittent or erratic signal. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
On diesel systems fitted with a secondary water-in-fuel sensor, sensor B monitors water at its filter-housing stage. P238E sets when the control module sees that signal become intermittent or erratic, often because vibration, moisture, or harness movement disrupts the connection.
Common causes
Most likely first.
- Intermittent contact at connector
- Connector with intermittent contact under vibration
- Harness routed against vibrating component
Symptoms
- Check-engine light on
- Water-in-fuel warning may be intermittent or unavailable
How to diagnose it
- Save freeze-frame data and monitor sensor B live data or warning status to catch a dropout while the fault is active.
- Locate sensor B at the secondary filter housing using vehicle service information and inspect its connector for looseness, corrosion, moisture, or pushed-back pins.
- Check the harness route for chafing or contact with vibrating parts, then gently move it while watching the sensor reading.
- Test continuity and terminal contact in the sensor B signal, supply, and ground circuits while flexing the harness, following the wiring diagram.
- If the circuit remains stable, test sensor B and its installation using the manufacturer’s procedure.
Common fixes
- Secure the sensor B connector and restore proper terminal contact.
- Clean corrosion or moisture from the connector and repair damaged seals.
- Repair chafed or damaged wiring and secure the harness away from vibration.
- Replace sensor B if it drops out despite a sound circuit.
Can I keep driving?
Treat the water-in-fuel warning as intermittent or unreliable and avoid extended driving until sensor B feedback is stable. A missed water warning can allow water to damage the diesel high-pressure pump and injectors.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.