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Tips and advice

Car dashboard warning lights: the complete guide

Warning light appeared on your dashboard? We cover what you need to know

Modern cars use a series of dashboard warning lights to alert the driver to any issues, and it’s important to understand what they mean. 

Whether one pops up unexpectedly, or if it’s been lingering in the corner of the dashboard for some time, it’s worth investigating what the symbol represents. There's a chance that it could indicate a serious problem, like an engine issue signified by an engine management light.

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That being said, not all warning lights spell doom and disaster – it could be as simple as a door that’s not shut properly. A quick way to determine the severity of an issue is to check the colour of the warning light. Generally, warning lights are split into three groups:

  • Blue and green – a system, such as the headlights, is turned on, and does not relate to a fault.
  • Amber – there is an issue with the car and, while it may still be drivable, the problem should be investigated as soon as possible.
  • Red – there is a serious issue that should be dealt with immediately.

If your car displays a red warning light, it’s best to stop as soon as it’s safe to do so, turn the engine off, then check the car’s manual for advice. Only if it is safe to proceed should you continue with your journey.

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When you turn on your car’s ignition, all of the dashboard warning lights should briefly illuminate. This is only to test that they’re functioning properly, and the majority should turn off once the engine is running.

Most car warning lights are universal for all makes and models of cars, making them easier to recognise for any driver. Their location on or around the dashboard can vary, however, and we’d still recommend looking at your car’s handbook to double-check what they mean.

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Read on to find out the meaning of the most common and important dashboard warning lights you might come across in your car.

Engine warning light

The engine warning light – sometimes called an engine management light (EML) – looks like the outline of an old-fashioned engine block. Our in-depth explainer covers the most common causes of an EML, but it relates to an issue with the engine itself. It will illuminate either amber or red depending on the make and model of car, as well as the severity of the issue. 

Even if your car sounds and feels normal to drive, it is essential to investigate the issue, as driving with an engine problem could lead to serious – and expensive – damage.

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There are many causes of an EML, from harmless sensor issues to complete engine failure.

Oil pressure warning light

The oil pressure light, shaped like an oil can, will illuminate if there is a drop in oil pressure in the engine. It’s one of the most serious dashboard warning lights, hence its red colour.

If this light comes on, you should stop driving immediately and have the problem investigated. Oil pressure is needed to keep oil circulating throughout the engine, providing vital lubrication to its moving parts. Lack of oil pressure can lead to complete engine failure if it’s not rectified.

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An oil pressure warning light could be caused by something as simple as low engine oil, in which case you should top the engine oil level up to the recommended amount. However, there could be a more serious oil leak or oil pump issue at play that a service centre would need to investigate.

Brake system warning light

The brake system warning light looks like an exclamation mark within a circle. It is triggered when the car detects an issue with the braking system, but this could be as simple as a handbrake being left on. If you release the handbrake and the light remains on, there is a serious problem and the car should not be driven. If it illuminates while driving, pull over safely and call for roadside assistance or arrange for the car to be taken to a garage.

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Potential causes of a brake system warning light include low level of brake fluid or a faulty pad wear sensor. However, it could also be a more serious issue with the braking system, and you shouldn’t risk driving any further. If the pedal feels spongy when you press it, or sinks all the way to the floor, then it’s easy to tell that a significant issue has occurred and the car should definitely not be driven.

Battery charge warning light

The battery warning light looks just like a car battery, with plus and minus symbols within a rectangle. It can indicate a number of things, all relating to the car’s battery and charging system.

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The light will trigger if the car’s electrical systems are not receiving enough voltage, usually caused by a faulty battery, or sometimes an issue with the car’s alternator. The latter is a serious issue that will need to be resolved by a professional, but it’s possible to test the health of your battery yourself if you suspect that to be the issue. Signs of a faulty battery include dim headlights, or if your engine is reluctant to start. 

Temperature warning light

The temperature warning light, styled after a thermometer in water, signifies that the engine is overheating or that there isn’t enough coolant (also called antifreeze) in the system. If this light appears while driving, you should stop the car immediately – running hot for too long can lead to total engine failure.

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It could be that the car’s radiator is leaky, clogged or broken – you’ll likely see coolant dripping out if this is the case. It could also be due to a faulty water pump. More serious is a blown head gasket, which can lead to catastrophic failure if you don’t turn off the engine immediately. White smoke from the exhaust could be a sign of head gasket failure.

Some cars may use a blue temperature warning light as well. This light means that your engine is cold, so it should only appear when you start your car after it has been sitting for a while. The blue light isn’t one to worry about, but it’s advisable not to push your engine too hard until it has disappeared.

Low-fuel warning light

Most drivers are familiar with the low fuel warning light. As the name suggests, it illuminates if you’re running low on fuel and looks like a fuel pump. The trigger point for this light is different for practically every make and model of car, but in any case, it’s designed to give enough warning so you can find a fuel station – you’ll usually have around 50 miles of range left.

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Running out of petrol won’t cause any mechanical damage, but stopping on the road due to running dry is an offence. If you run out of diesel, it’ll be necessary to bleed the air from the fuel lines and injectors before the engine will start properly. That means there’s more to do than simply top up from a jerry can.

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If you’re using more fuel than you’d expect, it could mean that you have a fuel leak (check the ground under your car; especially your driveway or parking space), or your car’s on-board computer (ECU) is telling the engine to use more fuel than it needs. A garage will be able to check this for you.

Tyre-pressure sensor warning

Since 2014, it has been mandatory for manufacturers to fit tyre-pressure monitoring systems (TPMS) to their new cars in the EU. This system monitors the amount of air in the tyres and can detect a drop in pressure. If it does detect a drop, it will let the driver know by illuminating the tyre-pressure sensor warning light – symbolised as an exclamation mark within a flat tyre.

This is important, because low tyre pressures can adversely affect braking and cornering, and a sudden drop in pressure can cause a dangerous blow-out at high speed. If the TPMS system alerts you to low pressure, you’ll need to check and inflate the tyre. If it has an obvious puncture, you’ll have to change the wheel or use a puncture repair kit.

Traction-control warning light

You’ll most commonly see your car’s traction-control warning light when the wheels lose grip, usually in the rain or snow. It gives a visual indication that you’re close to the limit of grip. If it’s on constantly, it usually means it’s deactivated – either by a fault or by you switching the system off. If it’s the former, you’ll need to get the system checked, if it’s the latter, we recommend that you switch the system back on – check your car’s manual to find out how to do so.

Glow plug warning light (diesels only)

The glow plug warning light is exclusive to diesel cars and looks like a coil of wire. It will almost always illuminate before starting the car, a normal procedure as the glow plugs warm up the engine’s combustion chambers. If it illuminates while driving, it could indicate that something’s wrong with the plugs themselves or the systems and computers that control them. 

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You may not notice anything wrong at first, but issues with glow plugs can cause combustion to occur slightly too early or too late (known as ‘knocking’). This likely won’t cause any damage to the engine, but it will make your engine sound a bit rough and not run as smoothly or efficiently as it should, resulting in a drop in fuel economy. You should take your car to a garage to investigate the issue.

Seatbelt warning light

These days, the vast majority of new cars come with a system to let you know if any of your passengers haven’t got their seatbelts fastened. There’ll usually be a light – as above – to tell you if this is the case.

Cars use pressure sensors in the seats and sensors in the seatbelts – so if there’s a certain amount of weight on a seat and the seatbelt isn’t secured, it’ll let you know. These warnings may be accompanied by an unusual noise, too. If the light remains on with no passengers or luggage on the seats, then a faulty sensor or seatbelt buckle is probably the culprit.

Door/boot/bonnet warning lights

Like the seatbelt light, these lights don’t usually mean that there’s anything physically wrong with the car (unless the sensor that sends the signal to the light is itself faulty). Instead, they tell you that one of the openings – be it a door, boot or bonnet – is open.

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This is often obvious if, for example, you’re putting the weekly shop into the boot or securing your children in the back seats. But these lights also tell you if a door, boot or bonnet hasn’t been shut properly and is only loosely closed, so they can be very useful.

Hybrid and electric vehicle warning lights

Hybrid and electric cars feature some systems and technologies that aren’t found in traditional petrol and diesel cars. As a result, there are new dashboard warning lights that you may not have come across before. The following examples appear exclusively in hybrid and electric vehicles.

Ready to drive warning light

Unlike a standard petrol or diesel, a hybrid or electric vehicle will be virtually silent when starting up. To avoid any confusion, this light simply informs you that your car is ready to be driven, so there is no cause for concern.

Limited power warning light

This warning light is shaped like a tortoise. It may look friendly, but it actually means that your vehicle is running on limited power. There are a number of faults that could be causing this lack of power and they vary in severity, but it can also indicate a very low charge in the battery, and is limiting your power to help you get to a safe place before energy runs out completely. It’s best to stop the car in a safe place and arrange for it to be taken to the garage for a diagnosis.

Battery charge level warning light

This light will appear in your hybrid or electric car if the battery is at a critically low level of charge. If you do not stop the vehicle soon, you could end up stranded. The best, and most obvious, course of action is to seek the nearest available charging point, whether this is at home or a public facility. 

This warning light is different to the battery warning light mentioned earlier, found in petrol and diesel cars.

Pedestrian alert system

This symbol looks like a loudspeaker next to a car. Because electric and hybrid vehicles can be so quiet, especially at low speeds, it can be difficult for pedestrians to hear them approaching. In order to prevent any accidents, these vehicles are usually fitted with a system that emits a sound to alert pedestrians to your presence, without the aggression of using the horn. If this light stays illuminated, regardless of your speed, then there is a fault with this system. This will require a dealer visit in order to determine the problem.

Drive a diesel car? You’ll want to read our guide to AdBlue…

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Charlie writes and edits news, review and advice articles for Carbuyer, as well as publishing content to its social media platforms. He has also been a regular contributor to its sister titles Auto Express, DrivingElectric and evo. As well as being consumed by everything automotive, Charlie is a speaker of five languages and once lived in Chile, Siberia and the Czech Republic, returning to the UK to write about his life-long passion: cars.

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