Car warning lights: understanding dashboard symbols and their meanings

Long gone are the days when a car dashboard only provided speed, fuel and temperature readouts. Today’s models use increasingly sophisticated technology designed to deliver the driver ever more information – usually – in a straightforward way.

The myriad warning lights and symbols are intended to give you an easy indication as to the health of your car and its functions. Heeding them will help you stay safe.

Car warning lights generally indicate the severity of a situation through a traffic light-inspired system:

- Green lights illuminate when a system is active and working as it should
- Amber or yellow lights highlight issues that will soon require attention, and caution is needed
- Red lights are alerts that there’s a serious problem that needs immediate attention

As cars become more complex and feature-packed, so too do the car’s sensors and onboard diagnostic systems. Quite simply, when there’s a fault, a warning light should shine. On some occasions, these might be triggered by a fault with the sensors themselves, but you should always remedy the problem or seek advice if you see an amber or red light.

Some of the most important warning lights to be aware of include:

- Check engine light
- Oil pressure warning
- Battery/charging system indicator
- Brake system warning
- Coolant temperature light

Regardless of which lights you see, don’t ignore it, because it could end up costing you far more in repair costs and time off the road if you do. Your car’s manual will provide you with more information, or you can call your local garage or dealership for advice.

It's worth noting that not all of the warning lights we've covered here will appear on your car – there's no oil pressure light on an electric car, for example, and no glow plug warning lights in anything not running on diesel.

Types of car warning lights: red, yellow, and green

Below we outline some of the issues you might encounter when you see a warning light, and the colours you can expect them to be. Remember, green is the least serious, red will require urgent attention.

Red warning lights

The most serious warnings come from red lights. These indicate immediate attention is needed, and you should stop driving as soon as it’s safe to do so. Examples include:

- Brake system fault: this light can be triggered by low brake fluid or other serious issues with your car’s braking system.
- Engine temperature warning: an overheating engine can cause serious damage, especially if your coolant levels are low.
- Airbag warning: airbags are a safety-critical feature, and the presence of the warning light means your car’s airbags could fail to deploy in a crash. Note, depending on the car, these can be red or amber.

Yellow or amber warning lights

If you see a yellow or amber warning light, it’s an indication that something needs attention, but it’s not immediately critical. These can include:

- Check engine light: also referred to as the engine management light, this indicates a range of engine-related issues. If you see a solid light, faults are usually at the minor end of the scale; a flashing light indicates something slightly more serious. Either way, you’ll need to take it to a garage to be checked.
- ABS warning: this shines when there’s a problem with your anti-lock brakes. Although your brakes will still be functional, a lack of ABS can increase your stopping distances in an emergency. As an important safety feature, you should get it addressed as a priority. 
- Tyre pressure monitoring system (TPMS): if your car’s tyre pressures drop below a set level, the TPMS light will illuminate. You should check your tyre pressures and inflate them as needed before re-setting the TPMS system.
- DPF warning: the diesel particulate filter (DPF) is designed to trap soot from the exhausts of diesel vehicles. Occasionally they can become clogged, triggering the warning light.

Green warning lights

It’s arguable whether green lights are warnings at all, because they’re typically just there to provide information about some of the systems operational in the car. These include:

- Indicators: typically you’ll see green arrows flashing to remind you if your indicators or hazard warning lights are flashing
- Headlights: operational sidelights and dipped headlights will be shown through different green symbols. Main beam operation is usually indicated by a blue light.
- Cruise control or speed limiter: icons with tiny speedometers are shown when cruise control or speed limiters are active. These may be accompanied by the speed you’ve set.

Common red warning lights and their meanings

Here are some of the critical red warning lights you might see. If these illuminate, you should stop the car as soon as it’s safe to do so and seek advice.

Brake system warning light

This one’s obviously important, which is why the light itself is a red exclamation mark. It might just mean you just haven’t fully released the handbrake, so make sure it’s completely off before you get too worried. The light can point to a more serious problem with the braking system, though, and you really don’t want to take any chances, so have the car inspected as soon as possible if it comes on. 

Oil pressure warning light

A red symbol that looks like a dripping watering can is arguably the most serious warning light after brakes. It can mean the engine’s oil level is too low, the temperature is too high or the oil pressure is too high or too low. All of those things are bad news for an engine and can lead to serious mechanical damage, so seek help straight away.

If the light comes on while driving, stop as soon as it's safe and turn off the engine. Check the oil level, but don’t restart the engine if the level is too low. You may need to be towed to a garage for inspection.

Engine temperature warning light

A red thermometer, shown in the image above, in water means your car’s engine is getting too hot and there’s a problem with the cooling system. The coolant might be running low and simply need a top-up (check the gauge on the coolant reservoir under the bonnet first), and it’s always best to do this when the engine is cold. Don’t rule out a leak in the system, either. This warning light can also point to much bigger problems, such as a broken radiator, water pump or head gasket.

If you see this light, safely pull over and turn off the engine to allow it to cool sufficiently before checking the coolant levels. Never remove the radiator cap while the engine is hot. If the light remains on after adding coolant, have the vehicle towed to avoid further damage.

Power steering warning light

If you see a steering wheel, possibly with an exclamation mark beside it, that means there’s a fault with the car’s power steering. If the system fails completely, it doesn’t mean you won’t be able to steer at all, but the steering will become much heavier, which will make it more difficult to manoeuvre the car.

Seatbelt warning light

It’s an obvious one, but a red image of a strapped-in passenger suggests someone isn’t wearing their seatbelt – and you’ll probably hear a bonging noise as well. Modern car seats are fitted with pressure sensors that trigger warning lights and sounds when they detect a certain amount of weight in the seat. However, putting heavy items in the seats can also set them off unnecessarily.

What to do if you have a red warning light?

When faced with any red warning light, it's crucial to act quickly and decisively. While some issues may allow for a short drive to a nearby garage, others will require you to stop immediately. 

Yellow and orange warning lights explained

ABS (Anti-lock braking system) warning light

If your ABS light illuminates, it means your anti-lock braking system (ABS) isn't working correctly. It doesn't mean that your brakes have failed, so the car should come to a halt in normal conditions. However, ABS is designed to prevent your car from skidding when you're braking hard or on slippery surfaces. If it's not working, it's a significant safety risk, so must be checked as soon as possible. An ABS light is an MoT failure.

Airbag warning light

An image of a seated passenger with what looks like a beach ball in front of them can point to a problem with the airbag system. Although it can also indicate that an airbag has been deactivated if a child seat has been installed, for example. But if you haven't deliberately deactivated the system, you should get the problem investigated, because it could point to a problem with this vital safety system.

You may also see a secondary warning light which provides an alert if a passenger airbag has been deactivated.

Battery/charging system warning light

The battery symbol is one of the more ambiguous warning lights. At its simplest, it can mean the battery is low on charge, which isn’t unusual if the car hasn’t been driven for a while. Low voltage on a car that is driven regularly can mean it’s time to replace the battery, though. The warning light can also point to other problems with the electrical and charging system, such as issues with the alternator or damaged wires or ignition cables, which can require a more involved diagnosis.  

Brake pad wear warning light

Some cars have a brake pad wear warning light, which is usually an orange circle with six dashes around the edges. This isn’t as urgent as the red exclamation mark, but it does mean that one or more of the brake pads is reaching the end of its life. It doesn’t need instant attention, but you should book the car in for replacement brake pads as soon as possible.

Check engine light

An orange or red light in the shape of an engine is one of the most vague warning lights, which means the engine control unit (ECU) has detected a problem. Exactly what that problem is can vary dramatically; it could be anything from a faulty sensor to a serious mechanical failure. So it’s a good idea to get the car checked out as soon as you can.  

Door or boot open warning

If you’ve left a door, the boot or the bonnet open, there isn’t anything wrong with the car, but it isn’t safe to drive off until it’s properly closed. The symbol itself is usually an image of a car with the corresponding body panel sticking out.  

DPF (Diesel Particulate Filter) warning light

The exact appearance of this light can vary, but it usually has a series of circles arranged in a rectangle to resemble an exhaust, and some add three semicircles designed to look like a cloud. The particulate filter on diesel-engined cars can become clogged and cause problems, particularly if you’ve recently done a lot of low-speed/stop-start driving. Driving for a time at higher speeds on the motorway should be enough to unclog the filter, but if the light doesn’t go away after that, further attention is required.

Glow plugs warning light

Glow plugs are specific to diesel cars; they help with combustion and are vital for getting the engine started when it’s cold. The glow plug warning light usually looks like a coiled piece of wire (shown in the right of our photo) and it will typically remain on for a few seconds after you’ve turned the ignition key as the plugs heat up, especially on cold mornings. If that’s all that happens, there’s nothing to worry about, but if the light stays on or illuminates later, there might be an issue with the plugs or the systems that control them.

Low fuel warning light

Without petrol or diesel in your fuel tank, your car’s engine will stop, so it’s critical to act on this light as soon as you can. Low levels of fuel in your tank can increase the risk of debris being sucked into the fuel system, which can cause all manner of fuel-supply problems. The warning can come from a single yellow bulb near the fuel gauge, or can be a yellow petrol pump — but they mean the same thing.

Traction control warning light

The traction control system helps to keep your car on the straight and narrow when its wheels lose grip. Sensors detect when the wheels are starting to spin and trigger a reduction in engine power and a small amount of braking to stop the car from sliding or skidding too much. When the system kicks in, a warning light that typically looks like a car with a pair of squiggles in front of it flashes. That’s perfectly normal and just means you might want to back off the accelerator a bit. It's possible to switch off most traction control systems, though, which will cause the light to remain on permanently. If you haven’t done that and the light stays on, the system might not be working properly.  

Tyre Pressure warning light

Tyre pressure monitoring systems have been mandatory for new cars sold in the UK since November 2014, and they were fitted to many models sold before then, so they’re a common feature. Sensors in the wheels monitor the amount of air in the tyres, and if you see a U-shaped warning light with grooves on the bottom and an exclamation mark in the centre, that means the pressures are too low. Topping the tyres up should sort it, but if the light comes back on, you might have a puncture or another problem.

Green and blue warning lights

Green warning lights

Green lights are usually there to indicate a function is working correctly, rather than providing a warning. Common green lights include:

- Indicators: these are usually green arrows which flash when the indicators or hazard lights are operating
- Cruise control/speed limiter: these are small illustrations of speedometers with small arrows that illuminate when the systems are engaged
- Auto start-stop: this symbol is usually a circular arrow with an ‘A’ in the centre which shines green when the system is active

Blue warning lights

In most circumstances, the only blue light you’ll see is when the main beam headlights are active. Some cars may also have a blue light that indicates that the engine hasn’t reached its operating temperature.

What to do when a warning light appears

Your car’s owner’s manual is invaluable when a warning light appears, because it’ll give you specific information on every symbol your car has – and what to do if a light comes on. Generally speaking:

- A flashing light usually indicates more urgency than a steady light
- Multiple lights can appear in combinations to provide more information about a fault

Depending on the fault, you may need to get some professional help from a garage or a dealership, particularly if you see a red light, or you have persistent or intermittent amber lights.

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Read more: Best emergency breakdown warning lights

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