semiatic

Master warning light (triangle with !)

A catch-all warning: the car has found a problem, often one with no lamp of its own, and has put a message about it on the driver display, usually with a chime or another lamp. The message, not the triangle, says what is wrong. Red marks a serious fault; amber or yellow marks something that needs attention.

RedYellow / amber

Not defined by regulation: a maker convention

What to do

Read the message on the driver display first. Red: stop where you can do so safely — Volkswagen says do not drive on; Renault says stop as soon as traffic conditions allow, switch off the engine and do not restart it, and call a dealer; Peugeot says stop, switch off the ignition and contact a dealer. Amber or yellow: Volkswagen says check the fault as soon as possible, and Renault says visit a dealer as soon as possible and drive with care until then.

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.

How urgent is it?

  • Red: Stop now. Volkswagen: do not drive on. Renault: stop as soon as traffic conditions allow, switch off the engine and do not restart it. Peugeot: stop as soon as it is safe to do so and switch off the ignition.
  • Yellow: Have it checked soon. Volkswagen: check the fault as soon as possible. Renault: visit an approved dealer as soon as possible; meanwhile drive with care.
Symbol
An exclamation mark inside a triangle
Also called
Master warning indication; Central warning lamp; STOP warning lamp (Peugeot)
Colour
Red or Yellow / amber
Standard
None — a maker convention, described here from 7 makers: Nissan, Hyundai, Mazda, Volkswagen, Renault, Peugeot, Toyota

Where makes differ

Nissan's 2023 LEAF has both colours: yellow when a message is shown, red when a warning is shown. Hyundai's 2025 Tucson lights it for faults in its assistance systems — Forward Collision-Avoidance Assist, Blind-Spot Collision-Avoidance Assist, Smart Cruise Control (faulty or radar blocked), LED headlights, High Beam Assist and the tyre-pressure monitor — and says to look at the cluster display for details. Mazda's Mazda3 shows it as an amber display indication. Peugeot calls its red triangle the STOP lamp: a serious fault with the engine, braking system, power steering or automatic gearbox, or a major electrical fault. Renault's red lamp that spells out STOP is a different light. Toyota's owner pages say a buzzer sounds and the light flashes when the master warning system detects a malfunction.

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.

Neither FMVSS 101 nor UN R121 lists a master or general warning tell-tale.

Other red maker lights

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 conventionImmobiliser (security) lightCar outline with a key inside it · also yellow / amber · maker conventionCharging cable connected lightA plug on a cable · maker conventionElectric drive system fault light (EV and hybrid)A car outline with an exclamation mark · also yellow / amber · maker conventionLow drive battery light (electric cars)A battery with plus and minus signs, stacked on more cells · also yellow / amber · maker convention

All red dashboard lights, regulated ones included

Other yellow / amber maker lights

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 conventionService due (spanner) lightA spanner (wrench) · maker conventionLow engine oil level lightOil can above a wavy level line · maker conventionFrost / icy road warning (snowflake)A snowflake · maker conventionLow washer fluid lightWindscreen with a dashed fountain of spray · maker conventionKey battery low lightKey fob beside a small battery · maker conventionImmobiliser (security) lightCar outline with a key inside it · also red · maker conventionReduced power (tortoise) lightA tortoise · maker conventionPedestrian warning sound off or faultyWalking figure with sound waves · maker convention4WD / AWD warning lightFour wheels joined by axles and a drive shaft · maker conventionSpanner warning light (a fault, not a service reminder)A spanner (wrench) · maker conventionFoot on brake light (press the brake pedal)A foot pressing a pedal · also green · maker conventionElectric drive system fault light (EV and hybrid)A car outline with an exclamation mark · also red · maker conventionLow drive battery light (electric cars)A battery with plus and minus signs, stacked on more cells · also red · maker convention

All yellow / amber dashboard lights, regulated ones included

Sources

No regulation defines this light, so it is described from 7 carmakers' own manuals or owner pages, each fetched and checked on the date shown:

Written in our own words; the makers' pages cover their own models only.