Warning lights: which mean stop now and which can wait

The symbols are largely standardised, and the colours follow a simple logic: red means danger or a fault that calls for immediate action. Yellow or amber means a malfunction that needs looking at soon. Green and blue are information — lights on, cruise control active — not warnings.

When the ignition is switched on, most warning lights come on briefly and go out again after starting. That is a self-test, and a useful one: a light that does not come on at all may be faulty or deliberately disabled — a reason to ask questions when buying used.

What a symbol means on a particular car is set out in the owner's handbook, and that is the authoritative source. Manufacturers do not always use the same colour for the same urgency, and some lights change colour with the severity of the fault. If the handbook is no longer in the glovebox, the manufacturer often has a digital version.

Red lights report conditions in which driving on makes the damage worse or puts safety at risk. The rule is therefore simple, if inconvenient: hazard lights on, stop somewhere safe, engine off, and only then think.

These lights require you to park the car somewhere safe and not drive on until the cause is clear:

On many emissions-related faults the engine management light stays on steadily in amber — an appointment within the next few days is then usually enough. If it flashes, however, it generally reports misfires, where unburnt fuel reaches the catalytic converter and can overheat it. Then the rule is: ease off, drive to the nearest workshop without full throttle and at low revs, or stop.

The same principle applies to other lights: a light that flashes or changes from amber to red is telling you the situation has become more serious. Read the accompanying message in the display, if there is one.

Amber means a system is reporting a fault or a condition that needs attention but no immediate danger. The car can usually still be moved safely, often with limitations you should know about.

Amber lights generally allow you to drive on, but not to ignore them:

Newer cars show a text alongside the light, and it is often more precise than the symbol: “you may continue”, “visit a workshop”, “stop, switch off the engine”. Read it in full before deciding, and photograph it — the exact wording helps the workshop.

Some faults put the car into limp-home mode: less power, restricted gears, limited speed. That is a protection programme meant to get you to a workshop, not an invitation to push the appointment to next month.

Before you call breakdown assistance or the workshop, a quick look is worthwhile. Not to repair anything yourself, but to be able to say more on the phone than “something lit up” — and sometimes to find that the cause is harmless.

A few things can be checked without tools and without risk, and sometimes they save the call altogether:

With a red light pointing to oil pressure, temperature, brakes or steering, you do not drive on, not even to the next exit if it can be avoided. That is what breakdown cover from your insurer, the manufacturer or a motoring club is for. How to handle a breakdown abroad is covered in a separate guide.

With amber lights, context decides: if the car drives normally, no noises or smells have appeared and the text says “you may continue”, an appointment in the next few days is the right course. If any of that changes, so does the answer.

Behind every light there is an entry in the fault memory, and it is more precise than the symbol. What a fault code says, what it does not, and why clearing it is no repair is covered in the guide on fault memories.

For a booking request to a workshop that means: name the light, its colour, whether it flashes, the text in the display and the circumstances in which it came on. With that information a business can judge whether you should come in today or whether next week will do.