Water in Fuel Indicator
Indicates the presence of water in the fuel system.
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What it means (plain English)
The engine control module (ECM) detects water in the fuel system that can cause fuel contamination and engine issues.
What the computer is actually seeing
The ECM monitors input from the water-in-fuel sensor, typically measuring voltage levels between 0.5V (no water) to 4.5V (high water level).
What a healthy reading looks like
Water-in-fuel sensors usually output 0V-0.5V for normal conditions and above 2.5V indicates possible water presence.
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. Check wiring and connector to the water-in-fuel sensor for any visible damage or corrosion. Is everything intact? (Yes: proceed, No: repair wiring/connector)
- 22. Clear the fault code and run the engine. Does the code come back? (No: monitor, Yes: proceed)
- 33. Measure the voltage at the water-in-fuel sensor connector. Is it between 0.5V and 2.5V? (Yes: likely a sensor issue, No: proceed)
- 44. Check the fuel for contamination. Is water present in the fuel? (Yes: address fuel contamination, No: suspect sensor or wiring issue)
- 55. Replace the water-in-fuel sensor if all previous steps indicate no external faults.
Common causes
- Faulty water-in-fuel sensor
- Poor fuel quality or contaminated fuel
- Damaged wiring or connector to the sensor
Typical repair cost
$$
Related codes
Frequently asked questions
Can I drive the vehicle with this code active?
Yes, but get it checked soon as it can lead to more severe issues.
Will this code return after reset?
If the issue isn't addressed, yes, it will return.
Why does this code sometimes appear with SPN 6341?
SPN 6341 indicates a low water level warning; these codes can appear together when monitoring the water level in the fuel.
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