Car dash warning lights: What do the symbols mean?
Is your car trying to tell you something? Don’t ignore dash warning lights - our guide sets out what they mean and how to deal with them.
- Find out what the different dash lights mean
- Know your TPMS from your DPF
- Can you sell a car with a warning light on?
You may not pay much attention to them, but dotted around your car’s instrument panel there’s an array of different coloured warning lights.
Hopefully, your warning lights generally don't light up or flash at you as you drive. If they do, it's important to know exactly what your car may be trying to tell you.
Car dashboard lights: what to look for
You'll find that several lights illuminate as soon as you turn the car on, showing that the relevant systems are working. They should then go off. If any remain lit or light up during your journey, then they demand your attention.
The lights are linked to sensors, so an alert can simply mean that the sensor is faulty or that it has detected a problem.
Don't assume that's the case, though. Ignoring a light could lead to serious damage, as well as your car failing its next MoT. So it's best to find out exactly what the problem is and then you can work out what to do - if anything - next.
Dashboard lights are colour-coded so you know how urgently you need to act. In general:
Red lights
Require immediate action and often relate to safety-critical systems. You should stop the car and investigate.
Orange/yellow lights
Highlight system errors, information on critical features or low fluid levels. These should be resolved as soon as possible and may need professional attention.
Green/blue/black/white lights
These are information messages and do not indicate a fault.
You'll probably be aware of the obvious ones such as the low fuel warning light or maybe the light that shows that the handbrake is on, so we've concentrated on some of the more obscure ones that you might not be so sure about.
Car dashboard warning lights
Click on any of the symbols below to jump to an explanation of what they mean and the best way to respond
Tyre pressure (TPMS)
What to do: Stop and check your tyres
MoT fail? Yes, if the sensor is faulty and the tyre doesn't just require more air
Every new car sold since November 2014 has had to have tyre pressure monitoring sensors (TPMS) fitted. If they detect low pressure in any tyre, this symbol with an exclamation mark will pop up on your dashboard. It could indicate a slow puncture, a sudden blowout, or just that your tyres need topping up with air.
The sensors aren't always perfect, so it still makes sense to check your tyre pressures regularly. And remember that many cars want you to reset the tyre pressure monitor once you've filled up the tyres to the set figure. Otherwise, the pressure may be fine, but the light may not go off.
Diesel particulate filter (DPF)
What to do: Either take a long, high-speed journey or drive to a garage as soon as possible
MoT fail? Yes
The DPF traps the soot produced by diesel engines to prevent it from being released into the atmosphere, and filters are increasingly being used in petrol cars, where they are known as gasoline particulate filters (GPF). They are a key weapon in the fight against pollution. However, diesel filters in particular can become clogged up if the car is driven predominantly on short or slow journeys, at which point you'll see this symbol showing a box containing dots.
If this is the type of driving you normally do, you may be better off with a petrol, hybrid or electric car. Petrol models are normally cheaper than diesel equivalents to buy (and petrol fuel is cheaper than diesel, too), so unless you do many longer journeys you'll probably save money by ditching diesel. Meanwhile, petrol-electric hybrids are typically most efficient around town as are electric cars, so if you can afford one of these, you won't need to worry about a DPF going wrong.
The soot can normally be burned off in a diesel car by driving at motorway speeds for several miles and working the engine reasonably hard - unless the DPF is too full. It’s a complex and expensive component so follow the instructions on trying to clear it in the manual or take the car to a garage to have it checked.
Check engine
What to do Take the car to a garage as soon as possible
MOT fail? Yes
Unlike most warning lights, this engine warning light is not specific to any one problem. The symbol of an engine outline could mean there’s a fault with all sorts of components and sensors. Most are related to the car’s emissions control system so a problem may not be apparent or urgent but you should get it checked as soon as possible.
Suffice it to say, if this comes up on your dashboard, don't delay. Get it checked as soon as you can, as you could be causing more damage by continuing to drive it if you don't do anything.
Engine oil level
What to do: Top-up the oil as soon as possible
MoT fail? No
As part of your regular maintenance checks, you should check the engine oil level using the dipstick in the engine bay or electronic readout (many cars show the oil level on the in-car computer). Fail to do so and there is a chance that the low level light could come on - when the quantity of oil in the engine is reaching a critical level - at which stage you could potentially be causing damage to the engine. The symbol of a dripping oil bottle is a sign that you need to top up.
Running the engine too low on oil can cause significant damage, so it's worth having the right type of oil (check which type in the manual) to hand, so if that if the light comes on you can top it up straight away. Better still, check the oil level every month or two and you shouldn't have to worry about the warning light coming on.
Brake pads worn
What to do: Reduce your speed and have the brake pads - and possibly discs - replaced as soon as possible
MoT fail? Yes
This symbol of a circle with dotted lines on the sides can be difficult to distinguish from that for the brake system. The dotted lines represent the brake pads - which grip the brake disc and slow the car down - showing that they are almost completely worn and should be replaced as soon as possible.
The more worn the brake pads are, the less effective they'll be at stopping the car, so you'll want to get this checked out as soon as you can. Fail to do so and it's likely that the car won't stop as quickly as you expect in an emergency.
Anti-lock brake system (ABS)
What to do: Reduce your speed and drive to a garage immediately
MoT fail? Yes
This system is a critical safety aid. ABS prevents the wheels from locking up under heavy braking and in slippery conditions, enabling you to retain steering control and brake in a shorter distance than would otherwise be possible. This symbol of a circle containing the letters 'ABS' is a sign that something is wrong, so the system should be checked.
Electronic parking brake fault
What to do: Drive to a garage immediately.
MoT fail? Yes
An electronic parking brake is a complex and expensive component. If the warning light, showing an exclamation sign in a circle with a line through it, comes on, take the car to a garage immediately.
If you need to stop the car and park it, there are a few things you can do: put it in first gear when facing uphill - or in reverse when facing downhill - if it's a manual. Or in 'Park' if it's an automatic. It's also worth turning the wheels into the kerb, too, as this will prevent the car from rolling far if the car isn't held in place.
Stop-start unavailable
What to do: Drive as normal. Check the battery if it's on permanently
MoT fail? No
This isn't normally a fault, but your car preventing itself from running the battery down in heavy traffic. The stop-start system automatically turns the engine off when the car is stopped (this happens when you put a manual car into neutral, or come to a halt in an automatic). The car then relies on the battery to power equipment such as the radio and air-conditioning, and to restart the engine when you go to move off again.
If electricity levels in the battery run low, stop-start is disabled until the engine can recharge the battery again and the symbol containing the letter 'A' with a line through it will light up. If this is lit permanently, it may indicate that your battery needs replacing, as it is incapable of retaining enough charge for the start-stop system to function.
Service
What to do: Book your car in for a service as soon as possible
MoT fail? No
Servicing your car on time is a mandatory part of many leasing and finance agreements - as the finance or leasing company is the owner of the car and requires it to be serviced on time to ensure the maximum value for the car at the end of the contract (well looked after, fully serviced cars are worth more than those that haven't been maintained well).
It's also a good idea to maintain your car well in general. This should ensure it is as reliable as possible and all the systems are running as efficiently as they can. Many cars will monitor the time and mileage covered since the previous service and alert you when the next is due with a spanner symbol.
Other vehicles use condition-based servicing, or variable service intervals. They monitor wear and tear on specific components, and then calculate when the next service is needed. You'll often see a service symbol with a mileage countdown, showing how far you can drive before the service is due.
AdBlue low
What to do: Top up your car's AdBlue tank
MoT fail? No
Modern diesel cars use an additive, called AdBlue, which is injected into the exhaust where it reacts with toxic pollutants and converts them into harmless air and water. If it runs out between services, then it must be refilled.
A yellow symbol of a bottle being poured is often used to indicate that the tank is running low. When it turns red, it needs refilling urgently; the car will fail to start if the AdBlue runs out completely. Not all manufacturers use a bottle. Others show what looks like an ice cream cone lying across a diesel particulate filter.
Fuel tank cap not fitted properly
What to do: Check the cap is secure or replace it
MOT fail? No
The humble fuel tank cap is a key part of the car’s fuel system since it helps to regulate the air pressure in the fuel tank and maintain an uninterrupted supply of fuel to the engine. If you've forgotten to replace it after filling up, your car should warn you with this unusual symbol that looks a bit like a screw being pulled out of a car.
Electronic stability control
What to do: Drive to a garage as soon as possible (when light is permanently on)
MoT fail? Yes
Unlike traction control, below, ESC, as it’s more commonly known, uses the brakes to keep a vehicle on the right path, without skidding. If you see the sliding car symbol flashing, then it’s in operation and the system has cut in to keep the car stable. When the light remains on, it’s likely to indicate a fault.
Electronic stability control/traction control off
What to do: If you didn't switch it off, have the system checked as soon as possible
MoT fail? Yes
This sliding car symbol applies to the Electronic Stability Control (ESC), which aims to keep the vehicle pointing in the right direction if the wheels start sliding left or right. Traction control, meanwhile, helps to prevent the wheels from slipping when you accelerate.
Many cars allow you to switch these systems off with a button, which illuminates this warning light. It's easy to see if you've switched it off by accident by pressing the respective button on the dashboard, and it should also light up if there's a fault that has disabled it.
Washer fluid low
What to do: Top up windscreen washer fluid
MoT fail? Yes
A low washer fluid symbol, showing a fountain of screenwash, can result in your car failing an MOT, although a good garage would top it up for you to ensure that a minor oversight doesn't require a retest.
More importantly, a lack of screenwash could leave you struggling to see, particularly in winter when the sun is low in the sky and road salt is splattered across your windscreen. As a result, it's very important to maintain a good level of screenwash in the car to avoid poor visibility through the windscreen causing you to crash.
Press clutch pedal
What to do: Push the clutch pedal
MoT fail? No
Modern manual cars generally require you to press the clutch pedal when you start the car, which helps to prevent it lurching forward if it's still in gear. If you're not used to this system, then you'll see this symbol of a foot in a circle appear in amber or green when you press your car's start button or turn the key. It may also appear if you stall a car with a push-button start system; depressing the clutch can restart the engine.
Automatic cars also use a similar symbol that instructs you to put your foot on the brake pedal before starting the car. In this case, there are brackets on the left and right of the circle, indicating that it's brake-related.
Tiredness alert
What to do: Take a break
MoT fail? No
Tiredness alerts are fast becoming a standard feature of cars. Most analyse your steering movements to detect when fatigue is setting in and the driver is less alert. The steaming coffee cup is a common symbol used to encourage you to take a break. The system doesn't prevent you from continuing to drive if you feel up to it.
Ice warning
What to do: Watch out for ice
MoT fail? No
The snowflake symbol tends to appear with a loud chime when the outside temperature drops below 3-4C. At this level, ice can form on the road, so it's a warning to be more cautious.
Key not detected
What to do: Ensure that your key fob is in the front of the car
MoT fail? No
Cars with keyless start will only switch the engine on if the key fob is close to a sensor in the front of the car. If you've left the key in a jacket that's been placed in the boot, you may see this alert of an exclamation mark over a key - telling you to bring the key fob closer.
The warning also helps avoid driving away without the key - if you're dropping off a passenger who has a key in their pocket, for example. The engine doesn't switch off without the key, so it would be easy to drive merrily away and park up, only to find out that you can't restart the car and you're miles away from the key.
Brake system fault
What to do: Stop and check the brake fluid level. If OK, drive at reduced speed to a garage
MoT fail? Yes
While you can still brake - just - with worn pads, a fault in the braking system itself could suggest total failure is imminent. This red symbol of an exclamation mark in a circle may indicate a fluid leak in the system, that the servo that provides the braking effort may be faulty or that the brake fluid level may have dropped.
If the brake pedal feels spongy, stop driving immediately, as continuing to drive could prove dangerous, with you unable to bring the car to a quick stop if needed.
Engine temperature
What to do: Stop the car immediately
MoT fail? No
This thermometer in water symbol means the temperature of the engine is too high either as a result of insufficient coolant in the system caused by poor maintenance, or potentially a broken water pump, a leaky radiator and hoses, or a blown head gasket allowing coolant to escape. Drive any further and you risk destroying the engine. It is also possible the light may come on in very hot conditions or if you're driving the car very hard for a sustained period of time.
Battery charge
What to do: If you can, drive to a garage immediately
MoT fail? No
This battery symbol applies not only to the battery but the whole of the vehicle’s electrical system, including the alternator that generates current. It’s serious because a modern car relies on electricity to power things such as the steering and brakes, as well as lights and the engine itself. If the battery is more than around four years old, it may be at fault.
Airbag and belt tensioner system
What to do: Take the car to a garage as soon as you can
MoT fail? Yes
The airbags and seatbelt pre-tensioners are key safety components which is why any issue with these should be checked and resolved as soon as possible. The symbol shows an airbag inflating in front of a passenger - not a pilates class.
Engine oil pressure
What to do: Stop the car immediately
MoT fail? No
Not to be confused with the low engine oil level light, which is amber, with a wavy line underneath the dripping oil can symbol, this one is much more serious, as it means oil isn’t being pumped around the engine. Drive any further and you risk destroying the engine.
Electronic power steering (EPS)
What to do: Stop the car and request assistance
MoT fail? Yes
Without power assistance, modern cars can be very hard to steer. If you see this warning light of a steering wheel with an exclamation mark, it's best to take no chances and stop in a safe place immediately.
Can I sell a car with a warning light on?
Some warning lights are easily fixed - it can just be a case of topping up fluids or filling up the tyres with the correct amount of air. If a sensor is at fault, then the fix can be simple too.
However, if the warning light indicates a failure of a major component, then it may be time to say goodbye to your car or you may be about to face a large bill.
Diesel particulate filters, for example, are fitted to most modern diesels and tend to be expensive to replace. MotorEasy, a used car warranty company, says that the most expensive DPF it has replaced is for the BMW 1 Series at £3145.
