Water in Diesel Fuel
Indicates the presence of water in the diesel fuel system.
Heads up: this code wasn't in our hand-written library yet, so DiagCoach AI built this page on the fly. Double-check critical specs against service info before condemning parts.
What it means (plain English)
The engine computer has detected water mixed in the diesel fuel inside the tank, which can cause poor engine performance or damage.
What the computer is actually seeing
The engine control module reads a signal from the fuel contamination sensor, indicating a higher than acceptable level of water in the fuel, typically above 0.5% volume.
What a healthy reading looks like
Normal water content in diesel fuel should be below 0.5% volume; anything above that triggers the fault code.
Guided diagnostic — the DiagCoach way
Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.
- 11. Inspect the fuel filter for water—drain any visible water and replace the filter if necessary.
- 22. Check the condition of the fuel tank; look for any signs of rust or corrosion that could indicate leaks.
- 33. Test the fuel quality; use a sample to check for excessive moisture with a water detection paste or testing kit - if above 0.5%, the fuel needs to be replaced.
- 44. Inspect the water separator and ensure it's functioning properly—replace it if necessary.
Common causes
- Contaminated fuel supply
- Failed water separator or filter
- Damaged fuel tank or lines allowing moisture in
Typical repair cost
$$$
Related codes
Frequently asked questions
Can I continue driving with this code?
No, it's not safe to drive as water in the fuel can cause significant engine damage or failures.
Will this code return after I clear it?
If the source of water contamination isn't addressed, it will return.
Why does this code sometimes pair with SPN 5200?
SPN 5200 is a generic fuel contamination signal; both indicate issues but with different severity or contexts.
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