What it means
The water-in-fuel sensor at fuel filter A has detected water above the warning threshold. The fuel filter must be drained; running the engine on water-contaminated diesel can damage the high-pressure pump and injectors.
At a glance
- Usually lights the check-engine light
- The engine or gearbox may go into limp mode
How it works
The water-in-fuel sensor at fuel filter A detects water collecting in the diesel fuel. This code sets when its signal indicates the water level has crossed the warning threshold, so the filter needs attention before contaminated fuel reaches the injection system.
Common causes
Most likely first.
- Water or condensation accumulated in the fuel filter
- Contaminated fuel
- Water-in-fuel sensor fault
Symptoms
- Water-in-fuel warning light on
- Check-engine light may illuminate
- Possible rough running or reduced power if fuel is contaminated
How to diagnose it
- Use a scan tool to review the code status and freeze-frame data, including whether the water warning was present continuously or intermittently.
- Check the fuel-filter A water warning and inspect its drain area for signs of accumulated water or fuel contamination.
- With the engine off, inspect the water-in-fuel sensor at filter A and its connector for corrosion, damage, loose fit, or fuel and water intrusion.
- Drain and inspect the filter contents using the vehicle manufacturer's procedure, then check whether the sensor reading changes.
- If the warning remains with a drained filter, test the sensor and its wiring against the manufacturer's specification before replacing parts.
Common fixes
- Drain water from fuel filter A and dispose of the contaminated fuel appropriately.
- Replace the fuel filter if contaminated fuel or water remains, or if the filter is damaged.
- Repair a loose, corroded, or damaged sensor connector or wiring.
- Replace the water-in-fuel sensor at filter A if it fails testing.
Can I keep driving?
Avoid driving while the water warning is active, especially under heavy load; water in diesel fuel can damage the high-pressure pump and injectors. If the engine runs rough or loses power, stop safely and have the filter drained before continuing.
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.