Dashboard warning lights: what's urgent and what can wait

The colour system

Most manufacturers follow a similar traffic-light approach. Red usually means a serious problem or a safety issue: stop as soon as it is safe to do so. Amber or yellow usually means something needs attention soon, but it is not normally an emergency. Green and blue are usually information only, telling you something is switched on, such as headlights or cruise control.

A light that flashes rather than staying on steady often means the problem is more urgent than the same light shown steadily.

Red lights: stop when it is safe

These are the ones not to ignore.

• Oil pressure (an oil can symbol). The engine may not be getting the oil it needs. Stop as soon as it is safe and switch the engine off. Driving on can cause serious engine damage.
• Coolant temperature (a thermometer in liquid). The engine is overheating. Stop safely and switch off. Do not open the coolant cap while the engine is hot, as it is under pressure.
• Brake warning (usually a circle with an exclamation mark). This can mean the handbrake is on, the brake fluid is low or there is a fault in the braking system. If the handbrake is off and the light stays on, get it checked before driving further.
• Battery or charging (a battery symbol). The charging system may have failed, and the car is running on battery power that will eventually run out. Head somewhere safe and get it checked.

Amber lights: get it checked soon

• Engine management (an engine outline). The ECU has logged a fault. Steady usually means book a diagnostic check soon. Flashing often means a misfire that can damage the catalytic converter: reduce speed and get it checked as soon as possible.
• ABS. The anti-lock braking system has a fault. Normal braking usually still works, but ABS may not, so drive carefully and get it checked.
• Airbag. There may be a fault in the airbag system, which means airbags may not deploy in a crash. Get it looked at soon.
• Tyre pressure (a horseshoe shape with an exclamation mark). One or more tyres may be under-inflated. Check pressures and look for damage or a puncture.
• Diesel particulate filter (on diesel cars). The DPF is getting blocked. Your manual will often suggest a sustained drive at steady speed to help it clean itself; if the light stays on, get it checked.

Why clearing the code is not a fix

Cheap code readers can switch a warning light off, and it is tempting to do just that. But clearing a code does not fix the fault behind it. If the problem is still there, the light will come back, sometimes after the fault has got worse. A light that has been cleared can also mean a car fails its MOT, since an illuminated engine light or certain other warning lights can be MOT failures in their own right.

A proper diagnostic check reads the code, looks at live data and confirms the actual cause, so you only pay to fix what is wrong.

What to do when a light comes on

• Note the colour, the symbol and whether it is steady or flashing.
• Notice anything else: noises, smells, smoke, loss of power or a change in how the car drives.
• For a red light, stop when it is safe and switch off. Do not keep driving to see if it goes away.
• Check your owner's manual for that specific symbol.
• Book a diagnostic check, and tell the garage exactly what you saw.

If you are in Blantyre or the surrounding area and are not sure whether it is safe to drive, call us during opening hours and describe what you are seeing. We will tell you honestly whether to bring it in or get it recovered.