Pay attention to your dashboard warning lights. They will alert you if your car’s mechanical or electronic systems aren’t working properly – and they can result in MOT failure if illuminated.
Warning lights can be split into three categories. Red usually means a serious problem, orange or yellow is advisory and blue or green cover everything else. Generally speaking, whether it’s a single light, or your dashboard is lit up like a shop window at Christmas, you should address the issue quickly.
This is an overview of dashboard warning lights and what they mean. For more detail, you may need to consult your car’s handbook.
Let’s deal with the red-light issues first – as you should when you see them.
Battery
A red warning light in the shape of a square car battery with positive and negative terminals indicates an issue with charging the battery.
This could be a problem with the battery itself, or the alternator or alternator belt. If the battery is failing to charge, you may be unable to start the car.
Brakes
A brake warning light could be triggered by something as simple as the handbrake being on.
If it doesn’t turn off when you disengage the handbrake, check the brake fluid level or ask a mechanic to investigate further.
Low oil pressure
A light that looks like an oil can signifies low oil pressure. You should not drive with this light illuminated, as it may cause damage to the engine.
Turn the engine off, open the bonnet and check the oil level using the dipstick – it may need topping up. Seek assistance if the light stays on.
Seat belt
A light showing a person sitting with a seat belt across their chest warns you that someone in the car is not wearing their seat belt.
If you don’t wear a seat belt and you haven’t got a valid reason, you could be hit with a £100 on-the-spot fine. The driver is also responsible for any children aged 14 or under not wearing their belts.
Coolant temperature
You should keep an eye on your car’s temperature gauge to identify any issues with its cooling system, but some cars also have a temperature warning light. This looks like a thermometer with wavy lines and indicates when the engine gets too hot.
Like the oil pressure warning light, you should stop and turn off the car’s engine to let it cool and prevent further damage.
Airbag
A light showing a person with a circle in front of them suggests there is a fault with one of the car’s airbags.
Investigate it as soon as convenient – a faulty airbag could compromise safety in the event of an accident.
Door open
This one is pretty self-explanatory. It could be one of the doors, the boot or the bonnet that is open, depending on the symbol shown.
If you see this light while driving, pull over safely and make sure the relevant door is closed.
Washer fluid
Let’s now move onto orange or yellow lights, which signify advice rather than an urgent issue.
A shortage of washer fluid can trigger a warning light on some cars. Simply top up the washer fluid reservoir to turn the light off.
Traction control
Occasionally you might see this light appear for a brief moment while driving. Most likely to illuminate in wet or slippery conditions, the traction or stability control light means the car is having to brake a wheel or cut power to prevent wheelspin or skidding.
Driving more cautiously, with the road and weather conditions in mind, should prevent it from appearing again. If the light stays illuminated, it may indicate a problem with the car’s traction or stability systems.
ABS
The ABS light is most likely to come on during hard braking. This is when the anti-lock braking system is triggered. During rapid deceleration, the system will modulate the brakes to prevent the wheels locking up and causing a skid.
As with traction control, if this kicks in on the road, adapt your driving – making it slower and smoother – to prevent it reappearing.
Engine management
The engine management or ‘check engine’ light could mean a wide range of things, from an open fuel filler cap to a serious engine problem.
You will probably need to plug a diagnostics reader into your car to establish exactly what the issue is.
Tyre pressure
If you car is fitted with a TPMS (Tyre Pressure Monitoring System), you may see this light when one or more of the tyres is under-inflated – possibly due to a puncture.
An under-inflated tyre will wear more quickly, lead to higher fuel consumption and cause the steering to feel sluggish. It may also make the car dangerous to drive.
If the TPMS light flashes for a minute or so when you start the car and then stays on, this means the system isn’t working properly. Get it checked at a garage as soon as you can.
Catalytic converter
A catalytic converter uses chemical reactions to break down harmful gases in your car’s exhaust system. This light means it is overheating or not functioning correctly.
You can continue driving with this light illuminated, but you should have the issue investigated promptly. If not, you risk further damage to the ‘cat’ – and a potentially bigger bill.
Service warning
The exact appearance of this warning light may vary, but it’s there to warn you that your car is due a service.
The service schedule will be detailed in the handbook, and you should follow it closely to keep your car safe and preserve its future value. Many modern cars will actually give you a mileage countdown until the next service is due.
Lane assist
If your car is fitted with lane assist – to nudge you back into lane if your car starts to drift on the motorway – a light might display to show it’s enabled.
Cruise control
Many cars are now fitted with cruise control, which helps to maintain a steady speed – and keep you within speed limits. Some systems use radar to maintain a set distance from the car in front, too.
A light showing a car’s speedometer with an arrow pointing at it might display when the cruise control is turned on.
Glow plugs
If you drive a diesel car, a glow plug light might display when you first turn the key. This means the glow plugs are warming up and the ignition shouldn’t be turned on until the light goes out.
If the light flashes, it suggests a problem with the glow plugs.
Bulb failure
Some cars will display a warning light when they detect a failed bulb in one of the exterior lights. Replace the bulb to extinguish the light.
DPF
If you drive a modern diesel car, it might display a DPF light when the diesel particulate filter becomes blocked.
This is most likely to happen if you drive lots of short journeys at low speeds. Allow it to regenerate by going for a long motorway journey.
Indicators
Now for the green and blue lights, starting with an obvious one.
When you turn your indicators or hazard lights on, left or right arrows will display on the dashboard to show which way you are indicating.
Main beam headlights
When you have got main beam engaged for driving in darkness, a blue light like the one pictured above will display on your dashboard.
You should make sure you dip your headlights when there are other cars about to prevent oncoming drivers being dazzled.
Fog lights
A curved ‘D’ shape next to wavy lines will indicate that your car’s front or rear fog lights are turned on.
These should only be used when visibility drops below 100 metres, as they can dazzle other drivers. They are not a substitute for headlights.
Stop/start
An exclamation mark below a curved arrow relates to the car’s stop/start system. Depending on the car, it could mean the system is activated, allowing the engine to turn off when the car is stopped to save fuel, or simply that stop/start is turned off.
It may also mean there’s an issue with the stop/start system – consult your owner’s manual if unsure.
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I had to drive around a lot the other day to run some errands, and I noticed that my check engine light came on towards the end. Thanks for explaining that this could be anything from an open fuel cap to a sign that your engine has a serious problem. I don’t really know anything about cars, so it would probably be smart to look into auto shops that can check my engine and see what’s going on for me.