Car warning lights explained: what to do when one comes on

By RPM Autocare, Newton Abbot · Published 26 October 2026

A light comes on, your stomach drops, and you wonder whether to carry on driving. Most dashboards show a mixture of symbols that are easy to confuse, and the meaning of the same symbol can vary slightly between manufacturers. This guide gives you a practical way to think about warning lights, and a rundown of the common ones. Your handbook is always the final authority for your car.

Start with the colour

Colours work like traffic lights on most cars:

• Red usually means a serious fault or a safety issue. Stop as soon as it is safe and find out why before driving on.
• Amber or orange usually means something needs attention soon. The car is often still driveable, but do not leave it for months.
• Green or blue is normally informational: lights on, cruise control active, and so on.

Then notice whether the light is steady or flashing. A flashing warning is generally more urgent than a steady one.

Lights that mean stop safely

Oil pressure. An oil can symbol, often red. It means low oil pressure, not simply low oil level. Stop as soon as it is safe and switch off. Running an engine without proper oil pressure can cause serious damage very quickly. This matters particularly on engines with a wet timing belt, where a flickering oil light can be an early sign of trouble. See our guides to Ford EcoBoost and PureTech wet belts.

Brake warning. Usually a red circle with an exclamation mark. It can mean the handbrake is on, brake fluid is low or there is a fault in the braking system. If it stays on with the handbrake off, or the pedal feels odd, do not drive on. Have it checked promptly.

Coolant temperature. A thermometer in liquid, often red. Overheating can wreck an engine. Pull over safely and let it cool before checking anything, and do not open a hot cooling system.

Battery or charging. A battery symbol. It can mean the charging system is not working, such as a failing alternator or belt, and the car may stop when the battery runs flat.

Airbag. A seated figure with a circle. It can mean part of the safety system is not working. The car may drive normally, but the airbags may not do their job, so get it looked at.

Lights that mean get it checked soon

Engine management (check engine). An engine outline, usually amber. Steady means a fault has been stored; get it checked soon. If it flashes, or the car is in limp mode or driving badly, stop and call a garage. See our diagnostics guide for what a proper check involves.

DPF warning. A box with dots, on diesels. It usually means the diesel particulate filter is filling with soot. Our DPF guide covers what to do.

ABS. The letters ABS in a circle. The normal brakes usually still work, but the anti-lock function may not. Have it checked, and take extra care in wet weather.

Glow plug. A coil symbol on diesels. If it stays on or flashes while driving, there may be an engine or glow plug fault.

Tyre pressure. An exclamation mark inside a tyre shape. Check pressures and for punctures; if the light remains after correcting them, have the system checked.

Power steering, traction control and others. Symbols vary by make. Look up the symbol in the handbook if you do not recognise it.

Lights people ignore (and shouldn't)

A light that comes on, goes off and comes back is still telling you something. Intermittent faults often get worse, and they are harder to trace the longer they are left. Write down when it happened and what the car was doing.

Another common mistake is relying on a light going out. If a fault is cleared and the light goes out, the problem has not necessarily gone. Warning lights can also stop working altogether if a bulb or circuit fails, so an unlit dash is not proof that everything is fine.

What to do when a light comes on

1. Note the colour and symbol, and whether it is flashing.
2. Check how the car feels. Any change in power, noise, smell or braking?
3. Red light or a car driving badly: stop safely, switch off and get advice. Do not carry on to see what happens.
4. Amber light and the car feels normal: check your handbook, then book a check soon.
5. Take a photo of the dash if you can; it helps with diagnosis.

If you are stuck, call a garage and talk it through. At RPM Autocare we have been known to come out to people in trouble, although we cannot promise a callout every time.

How we can help

Russ uses advanced diagnostic equipment to read the fault codes, then works out why the code is there, so you are not paying to swap parts until the light goes out. We can help with engine management, glow plug, ABS and airbag warning lights, limp mode and loss of power, faults that come and go, DPF warnings and rough running. You are told what was found, what it will cost and how urgent it is before work begins.

Visit our diagnostics page to find out more, or see car repairs for the work that follows. Whether you are in Newton Abbot, Kingsteignton, Teignmouth or Torbay, you can book in or contact us and tell us which light is on.

Related services: Diagnostics · DPF regeneration · Brakes · Repairs