Battery Charge Warning Light

When the ignition is switched on the battery charge warning light should turn on, and then off when the engine starts. If it doesn’t light up at all, or lights up when you are driving, there’s a fault with your charging system as the battery is not being recharged.

There could be a number of reasons to why a battery isn’t charging. Most commonly, there’s an alternator failure (a broken or loose alternator drive belt), or a slack starter terminal.

Diesel Particulate Filter Warning Light (DPF)

The purpose of a diesel particulate filter (DPF) is to trap pieces of soot in the exhaust. Just like any filter, it needs to be emptied now and again to maintain performance, which is called ‘regeneration’.

If your DPF warning light does turn on, it means that the filter is partially blocked, and you could be sending plumes of black smoke into the driver behind you. However by travelling at speeds greater than 40mph for 10-15 minutes, it should be possible to complete a full filter regeneration. If this light continues to stay on for longer than half an hour, as always seek professional assistance.

Diesel Particulate Filter Warning Light (DPF)

The purpose of a diesel particulate filter (DPF) is to trap pieces of soot in the exhaust. Just like any filter, it needs to be emptied now and again to maintain performance, which is called ‘regeneration’.

If your DPF warning light does turn on, it means that the filter is partially blocked, and you could be sending plumes of black smoke into the driver behind you. However by travelling at speeds greater than 40mph for 10-15 minutes, it should be possible to complete a full filter regeneration. If this light continues to stay on for longer than half an hour, as always seek professional assistance.

Engine Warning Light (ECU)

This light will turn on when the ignition is switched on, and should turn off when the engine starts. If the engine warning light begins to flash when you are driving, reduce your speed until it changes to a solid, illuminated symbol. If it continues to flash or turns red after you’ve reduced your speed then you should stop your car.

Important considerations

Try switching off the engine and waiting a few minutes before turning it back on, which will restart the ECU. If there are no other apparent faults with the engine, it is safe to continue driving while the ECU light is on, but it is important to have the vehicle checked by a garage or mechanic as soon as possible.

Handbrake Warning

This is a very familiar warning light for drivers, as it will turn on when the handbrake is engaged. However if the brake system warning light remains on after the handbrake is released, it could indicate low brake fluid.

Always refer to your vehicle handbook to ensure you add the correct amount of brake fluid, never exceeding the ‘max’ mark. You can tell when your brake fluid is low, as you’ll be able to press the brake pedal further than usual. However if the problem persists, even after you’ve topped up the brake fluid seek immediate assistance and do not continue your journey.

Oil Warning Light

When the ignition is switched on, the oil pressure warning light should turn on, and will extinguish once the engine starts. If the oil warning light remains illuminated after the engine has started, or lights up during a journey, you should stop and check the engine oil level immediately.

Why does an engine need oil?

Your engine needs oil to lubricate the moving parts inside, and it also provides a protective coating to these parts to prevent corrosion. Oil also facilitates the process of moving dirt and other particles to the oil filter, which can cause engine failure if it is ignored. It is important to remember that if the warning light remains on, even after you’ve topped up the oil, don’t turn on the engine and seek professional assistance.

Air Suspension Warning

The purpose of Air Suspension is to provide a smooth and consistent ride, however if the warning light appears there could be a fault in the air line, such as leaking pressure or a dryer failure, which removes the moisture from the air. Although not a serious problem it could cause damage to other parts of your vehicle over time, and should be addressed as soon as possible.

Airbag Warning Light

This is one of, if not the most important warning lights on your car’s dashboard. If an airbag is faulty, it could potentially not deploy in the event of a crash, significantly increasing the chances of injury. On the other hand, the airbag could also deploy unexpectedly, which could cause a crash itself.

If you get an airbag warning light, be sure to address the issue as a matter of urgency, as a driver’s safety should never be compromised.

Anti-lock Braking System (ABS)

If your car has an anti-lock braking system, the icon will light up when the ignition is switched on and turn off when the engine is started. However if it lights up when driving, that means the system has been deactivated because of a self-diagnosed fault.

Although normal braking (without ABS) will still be possible for most cars, it’s important to note that the front wheels could lock up when applying the brakes when the ABS is disabled, potentially sending the car into a spin. Always check your vehicle handbook if you’re presented with an anti-lock braking system warning light, as some cars will not be safe to continue driving.

Automatic Gearbox Warning

This light comes on to warn you that your gearbox is not working correctly. It stores a fault code in the ECU with information on what is wrong. Your car may go into limp mode in order to protect the engine/gearbox operation.

If this light is yellow then it means that action is required. If the light is red then you should stop the car as soon as it’s safe as more immediate action is needed.

Brake Lights Warning

Seeing this symbol light up in your car is an indication that your brakes lights are not working. You should check to see which of your car bulbs are broken and look to have them replaced.

Brake Pad Warning

When your car shows this warning light it means that your brake pads are worn and they may need replacing. A worn brake pad affects your cars ability to brake properly and it can lead to longer stopping times, while also damaging your car.

Possible symptoms and effects of worn brake pads can involve your car pulling to one side when you brake, your car making a metallic, growling sound and reduced responsiveness in the brake pedal.

Hill Descent Control

Hill Descent Control (HDC) works with your anti-lock braking system to give you greater control when you are in off-road situations or descending on steep gradients.

The indicator will illuminate constantly when conditions are met for the HDC to function. You will have to press the HDC button in your car first. When going down a steep gradient, if the HDC determines that your braking is insufficient to control the speed of your car then it will automatically take control of your brakes to maintain the correct speed.

Key Fob Battery Low

This warning light means that your Key Fob is running low on battery. It’s a good idea to replace the battery at the nearest convenient time from when see the warning appear.

They’re not too difficult to replace and you can pick up key fob batteries at a Halford’s or a chain supermarket like Sainsbury’s or Tesco’s.

Lane Departure Warning

A lane departure warning is a system that uses a camera at the top of your windscreen to monitor if your car is changing lanes without you indicating. If a driver is dozing off and their car is veering into another lane then the system will sound a warning to alert the driver, provided the system is turned on and the indicator is lit up.

Rain and Light Sensor

When the rain and light sensor comes on it is an indication that there is a fault in your sensor and you should have this checked.

Speed Limiter

A speed limiter will stop the car they are fitted in from going over a certain speed. The choice of top speed is set by the driver. This can be a benefit to a driver when they are going through areas where they need to stick to a specific speed limit.

Suspension Dampers

This indicator tells you that your car has an adjustable suspension. Your suspension can be adjusted via a controller inside your car to raise the vehicle up and down. Seeing this symbol light up on your dashboard likely means that you have a fault in your system which will require you to visit an auto shop.

Temperature Warning

When this symbol lights up on your dashboard it means that the temperature of your engine is too high. We advise you to stop your car at the nearest safe time to allow your engine to cool down. You should also switch your engine off. A further way to cool down you engine is to turn your heaters up to full to remove some of the engine heat.

This could occur because the coolant levels in your car are running too low. You should check the gauge on your coolant tank to see if it needs filling up. If this symbol goes well into the red then it could indicate that your car has a leak in the system which is letting out the coolant. Worst case scenario this symbol could mean a head gasket failure.

Water in Fuel Filter

If you see this symbol while you are driving then it means water needs to be drained from your fuel filter.

Diesel vehicles are equipped with separators that remove water from your fuel. These will need to be serviced at times and this symbol appearing indicates that you should service your car. However, if your car has just been re-fuelled then your fuel may be contaminated. This is when you should stop your car whenever it is safe to do so and then drain the filter bowl.

Make sure the engine is off when you drain the filter bowl as fuel can ignite if the separator is drained while the engine is on.

Airbag Deactivated

This informational symbol lets you know that the passenger airbag is deactivated, with the activate/deactivate option accessible by a small switch in the vicinity of the airbag itself, or through the interactive menu. For example drivers may want to deactivate airbags when a rear-facing child seat is fitted in the front passenger seat, you must remember to activate airbags when there is no child seat for your passengers safety.

Eco Driving Indicator

The Eco driving indicator will light up on your dashboard when you are driving in a fuel-efficient manner. It takes into account factors like acceleration, engine and transmission efficiency. By accelerating gradually, as opposed to slamming down on the pedal, you can keep your eco driving indicator on for longer.

This light can help you get more miles to the gallon as it trains you to be more environmentally conscious and more efficient in your driving, lowering your cost of driving.

Fault Problem

This symbol is a reminder that routine maintenance is needed on your car. Usually this symbol will appear in grey, however, if you see it in red then it means your car has a serious powertrain problem.

There isn’t too much you can do about seeing this symbol in your car other than take it in for servicing, it should then disappear.

Glow Plug/Diesel Pre-heat Warning

Diesel engines require heat in the cylinders to operate. This is supplied by the glow plugs when the engine is cold. This light will stay on until the engine is warm enough.

However, if this symbol doesn’t fade away then it usually means that a glow plug is wearing out. This can lead to starting problems with your car’s engine. Even if it is only one glow plug that has worn out it is advisable to get all the plugs replaced, especially as it can be quite an easy and cheap procedure to do.

Information Indicator

This indicator in your car displays that your car is warning you about any information you may have forgotten. For example it can remind you that your car door hasn’t been shut properly or you have low fuel in your tank.

Parking Assist

This symbol illuminates when you switch on your park assistance. When you are parking the system uses sensors to detect if your car is becoming too close to an object. The system should then give a warning noise or a display should appear if you are too close to an object.

You shouldn’t rely entirely on your car’s parking assist. You should still check all the way around your car for people and objects before reversing or accelerating into a parking space.

Service Required

When you see this symbol on your car’s dashboard your car is advising you to service your car soon. This indicates that you need a simple service.

Stability Control Off

If you see this symbol light up on your car’s dashboard then it indicates that your stability control system has been turned off. This simply means that the system will operate like a standard car would.

When your stability control system is left on the car will coordinate itself (brakes, engine etc.) in order to keep you on track when doing manoeuvres like cornering.

Winter Mode

The winter mode indicator on your dashboard warns the driver that frost or ice is present. The Sensors detect outside air temperature. The warning light symbol will illuminate amber when the air temperature outside the vehicle is between +4°c and 0°c. As the temperature falls below 0°c it will glow red.

Adaptive Cruise Control

Adaptive Cruise Control keeps your car at a safe distance from the traffic ahead and is usually found behind the front grill of a vehicle. It is very similar to conventional cruise control in that it maintains a vehicle’s pre-set speed, however it can also adjust speed with the aim of maintaining a safe distance from the car ahead. For example if a motorist cuts in front of you, or if you’re approaching a slower vehicle for example, the Adaptive Cruise Control will slow your vehicle down. The system will also re-accelerate the car back to the original pre-set speed when the road is clear.

Hybrid Ready Indicator Symbol

This symbol will only appear on your car if you own a hybrid. You could see either of these two symbols in your car but they mean the same thing. Their purpose is to tell a driver when a hybrid vehicle can move. It’s the eco-friendly person’s version of hearing their engine running. It’s a simple indication that your car has checked its parts and is ready to be driven.

Hybrid Ready Indicator Symbol

This symbol will only appear on your car if you own a hybrid. You could see either of these two symbols in your car but they mean the same thing. Their purpose is to tell a driver when a hybrid vehicle can move. It’s the eco-friendly person’s version of hearing their engine running. It’s a simple indication that your car has checked its parts and is ready to be driven.

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How well do you know your warning lights?

Cargiant knows that when you buy a used car the warning lights you see on the dashboard won’t always make sense. However, it really is always handy to know what they mean, so you don’t guess incorrectly and start to panic! So to help you out, we’ve created this interactive tool to give you the lowdown on each and every one of them. Challenge your friends to see who knows their dashboard the best.