Water in fuel light (diesel)
Water has collected in a diesel car's fuel system. The fuel filter separates water from the diesel and holds it at the bottom of the filter; when too much has built up, the light comes on, because water carried on into the engine can damage the fuel system.
Yellow / amber
Not defined by regulation: a maker convention
What to do
Have the water drained from the filter soon: Kia says driving on with the light on can damage engine parts and the fuel system. If it came on straight after refuelling, Volkswagen says to switch the engine off and call a repairer — the fuel you just bought may contain water. Otherwise reduce speed and drive with care to a garage.
Makes differ: what this light means on your car, the other colours it may use for the symbol and what the car wants you to do are set by the manufacturer, so your car's owner's manual is the authority.
- Symbol
- Fuel pump with water drops beside it
- Colour
- Yellow / amber
- Standard
- None — a maker convention, described here from 2 makers: Volkswagen, Kia
Where makes differ
Kia calls it the fuel filter warning light; Volkswagen calls it water in the diesel fuel tank and draws a fuel pump with drops. Both fit it to diesel models only.
Not defined by regulation: a maker convention
Neither US FMVSS 101 (Tables 1 and 2) nor UN Regulation No. 121 lists this light, so no rule fixes its symbol or its colour. What follows is what the makers cited below say; other makes, and other model years of the same make, may draw it differently.
The fuel level tell-tale is regulated (FMVSS 101 Table 1, UN R121 item 9); neither table has a water-in-fuel lamp.
Related lights a regulation does define
Other yellow / amber maker lights
All yellow / amber dashboard lights, regulated ones included
Sources
No regulation defines this light, so it is described from 2 carmakers' own manuals or owner pages, each fetched and checked on the date shown:
- Volkswagen: Volkswagen UK — Water in a diesel fuel tank (amber lamp) — There is water in the diesel fuel tank: reduce speed and drive with care to a repairer; if it lights immediately after refilling, turn the engine off and contact a repairer. checked 2026-09-24
- Kia: Kia UK — Dashboard warning and indicator icons (PDF) (Fuel Filter Warning Light (Diesel Vehicles Only)) — The filter separates water from the fuel; if the light stays on after starting or comes on while driving, water has accumulated in the filter, and driving on can damage engine parts and the fuel system. checked 2026-09-24
Written in our own words; the makers' pages cover their own models only.