semiatic

Warning lights no regulation defines: DPF, AdBlue, EPC, lane assist

Find it by its colour, then its shape. 1. Pick the colour the light glows. 2. Match the drawing. These 16 lights are maker conventions: no US or UN rule fixes their symbol or colour, so each one is listed only where at least two carmakers' own manuals describe it, and its page cites them.

Not defined by regulation: a maker convention

Tap a colour to see only those lights.

Red · 5 lights

Red asks for action now: stop where you can do so safely and find out what it means. Volkswagen's pages say to stop the car as soon as it is safe; SEAT's says to pull over and contact a retailer.

AdBlue (DEF) warning lightLiquid container with a wavy fill line and a drop · also yellow / amber · maker conventionForward collision warning lightCar seen from behind with radar arcs around it · also yellow / amber · maker conventionPower steering warning light (EPS)Steering wheel, sometimes with an exclamation mark · also yellow / amber · maker conventionDoor open lightCar seen from above with a door open · maker conventionHill descent control lightCar pointing down a slope · also green, yellow / amber · maker convention

↑ Pick a different colour · regulated red lights

Yellow / amber · 15 lights

Amber or yellow means a system is off, limited or faulty. Volkswagen's pages call it 'action is required'; SEAT's says urgent attention is not needed, but follow it up soon.

Diesel particulate filter (DPF) lightBox full of dots with a pipe at each end · maker conventionAdBlue (DEF) warning lightLiquid container with a wavy fill line and a drop · also red · maker conventionEPCEPC (electronic power control) lightThe letters EPC · maker conventionLane assist (lane keeping) lightLane markings running away from you, dashed line in the middle · also green · maker conventionForward collision warning lightCar seen from behind with radar arcs around it · also red · maker conventionBlind spot monitor lightTwo cars side by side with signal waves between them · maker conventionAdaptive cruise control (ACC) lightSpeedometer dial with a needle · also green · maker conventionAUTOHOLDAuto Hold lightThe words AUTO HOLD · also green · maker conventionPower steering warning light (EPS)Steering wheel, sometimes with an exclamation mark · also red · maker conventionWater in fuel light (diesel)Fuel pump with water drops beside it · maker conventionGearbox (transmission) warning lightCog wheel with an exclamation mark · maker convention?Key not detected lightKey with a question mark · maker conventionBulb failure (exterior light) warningLight bulb with rays and an exclamation mark · maker conventionHill descent control lightCar pointing down a slope · also green, red · maker conventionAAuto stop-start lightLetter A inside a circular arrow · also green · maker convention

↑ Pick a different colour · regulated yellow / amber lights

Green · 5 lights

Green is for information only, in both Volkswagen's and SEAT's wording: a system is switched on or working.

Lane assist (lane keeping) lightLane markings running away from you, dashed line in the middle · also yellow / amber · maker conventionAdaptive cruise control (ACC) lightSpeedometer dial with a needle · also yellow / amber · maker conventionAUTOHOLDAuto Hold lightThe words AUTO HOLD · also yellow / amber · maker conventionHill descent control lightCar pointing down a slope · also yellow / amber, red · maker conventionAAuto stop-start lightLetter A inside a circular arrow · also yellow / amber · maker convention

↑ Pick a different colour · regulated green lights

No blue here: of the regulated lights, blue is the high beam indicator, and on some cars a blue coolant thermometer meaning the engine is still cold (UN R121 note 18). None of the maker lights below uses blue in the manuals we checked.

What this page cannot do

These lights are maker conventions: the symbol, the colour and even the meaning vary between makes and between model years of the same make, and a light that is not listed here may still be on your car. This page cannot identify your exact model's lamp. Your owner's manual is the authority.

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.

Not here? The 30 lights the regulations do define — brake, oil, coolant, battery, airbag, ABS, tyre pressure and the rest — are on the main dashboard chart.

Left out, and why

Before a light was added here it was checked against FMVSS 101 Tables 1 and 2 (1 October 2025 CFR edition) and the table 'Symbols, their illumination and colours' of UN Regulation No. 121. A light either table defines belongs on the main chart, not here.

Checked against: govinfo — 49 CFR 571.101 (FMVSS No. 101), 1 October 2025 edition, Tables 1 and 2 as printed — checked 2026-09-24; Japan Ministry of Land, Infrastructure, Transport and Tourism — UN Regulation No. 121 (English and Japanese), table of symbols, items 1 to 44 — checked 2026-09-24.

Sources

Every maker page cited on these 16 light pages, each fetched with a plain request and checked on the date shown. Each light's own page says which rows it rests on.