Dashboard warning lights: which ones mean stop now.

When a light comes on, the first question is whether you can carry on driving. The honest answer starts with colour, then the symbol. Warning light symbols vary between manufacturers and models, so your handbook is the final word for your car. This guide gives a sensible way of thinking about them.

The colour code

Most cars use a broadly similar system:

• Red: a serious fault or a safety-critical warning. Stop as soon as it is safe, and do not carry on until you know why.
• Amber (yellow or orange): something needs attention soon. The car can usually be driven carefully, but do not ignore it.
• Green or blue: information, such as lights on, cruise control or main beam.

Some warnings are accompanied by a message on the dash or a chime. Read it. It often tells you what the car wants.

Red lights: stop and think

Oil pressure (an oil can symbol). Stop as soon as it is safe and switch off. Running an engine with low oil pressure can wreck it within minutes. Check the oil level once the engine has had a few minutes to settle. If the level is fine and the light stays on, do not drive it.

Engine temperature or coolant (a thermometer in waves of liquid). The engine is overheating. Pull over safely and switch off. Do not open the radiator or expansion tank cap while hot. Driving an overheating engine can cause serious damage, such as a blown head gasket.

Brake system (an exclamation mark in a circle, often with the word BRAKE). First check the handbrake is fully released. If the light stays on, it can mean low fluid level or a fault in the system. Treat it seriously, avoid driving if the pedal feels soft or different, and get the car looked at.

Battery or charging (a battery symbol). The charging system is not working properly. The car is running on the battery alone and will eventually stop. Switch off non-essential electrics and head somewhere sensible, not a long journey.

Airbag or seatbelt. An airbag fault light is not a "stop now" warning like the others in this section, but the airbags may not work as designed in a crash, so do not leave it. A seatbelt reminder is just that.

Power steering can show red on some cars, meaning heavy or lost assistance. The car can usually still be steered, but it will be much harder work, so pull over when it is safe and get it checked rather than carrying on.

Amber lights: act soon

Engine management (an engine outline). A steady light means the car has detected a fault, often related to emissions or sensors. The car may run normally, but it should be investigated. If it flashes, treat it as urgent, as a flashing light often means a misfire that can damage the catalytic converter. Ease off, avoid heavy throttle and get it checked as soon as you can.

ABS. The normal brakes still work, but the anti-lock function may not. Drive with extra care and get it checked.

Stability or traction control. A flashing light while driving means the system is working on a slippery surface. A steady light can mean it is off or faulty.

Diesel particulate filter (DPF). The filter is filling with soot. Some cars need a longer drive at steady speed to clear it. If the light stays on, do not ignore it, because it can lead to limp mode or an expensive repair.

Tyre pressure (TPMS). One or more tyres are low, or the system has a fault. Check pressures at the first opportunity. A flashing then steady light often points to a system fault.

Glow plug (a coil symbol on a diesel). While starting, this just means wait. If it stays on or flashes while driving, there is a fault.

Service due or oil level. Information about maintenance; do not leave it for months.

A flashing light is a sign to pay attention

Many lights behave differently if they flash instead of staying on. A flashing engine light is more serious than a steady one, and a flashing traction control light is normal on a slippery road. If you are not sure, treat flashing as urgent until you know more.

Lights that come and go

An intermittent light is still a light. A warning that appears on a cold start and clears, or only shows over bumps or in the wet, is the car telling you something is borderline: a sensor, a connector, a battery or a weak earth. It is tempting to wait until it stays on, but a fault that is easy to find while it is happening can be harder to find once it has gone. Make a note of when it appears (cold, hot, wet, after fuelling) and tell whoever looks at it.

What to do if a light comes on

1. Stay calm. Read any message on the dash.
2. If it is red, stop safely as soon as you can.
3. Check the basics: fuel cap tight, oil and coolant levels (engine cold), handbrake released, tyre pressures.
4. Look in the handbook for that symbol.
5. If you are unsure, do not drive on and hope. Ask for advice.

Why clearing the fault is not the fix

Lights can sometimes be cleared by disconnecting the battery or using a code reader. That does not fix the cause, and it can hide a problem. A fault code is a starting point for diagnosis, not a complete answer. The right sensor may be reporting accurately about a different fault, so code reading alone can lead you to replace parts you did not need to.

The short version

• Red means stop when safe.
• Amber means get it checked soon.
• Flashing means take it more seriously.
• Your handbook is the authority on your car.

Talk to us

If a light is on and you are not sure what it means, our diagnostics page explains how we find the cause. Call us on 07746 922 273 and we will tell you whether it is safe to drive in.