Dashboard Warning Lights: Most important lights explained

You might have heard the phrase ‘the dashboard lit up like a Christmas tree’ when someone is colourfully recounting an anecdote about that time their motor went into meltdown at the side of the M50. And this idiom relates to the sheer baffling number of warning symbols that can flash up in your vehicle’s display. Here, we look through some of the most common (and universal!) ones you might spot, to tell you what they mean and how you should go about rectifying them…

1. ADBLUE WARNING LIGHT

Many modern diesel cars are fitted with AdBlue tanks in order to meet emissions regulations. AdBlue is an exhaust additive that removes harmful NOx gases from diesel emissions, but it’s a fluid you need to keep topped up, otherwise your car’s engine management system will not allow the engine to run. This is a Volkswagen Group product’s ‘Low AdBlue’ warning, but it will be a similar icon/message on all relevant cars.

2. AUTONOMOUS EMERGENCY BRAKING (AEB) TRIGGERED/FAULT

AEB goes by many brand-derived names from car make to car make, but it is almost a prerequisite of all new cars (and has been for a few years now) if they want to get the highest Euro NCAP safety rating. This logo means your AEB isn’t working, which means the car won’t detect a stationary object in front of you and won’t automatically apply the brakes. It can also show up if the AEB is triggered, in the event you’re not paying 100 per cent attention to the road and the car feels it has to intervene and brake to avoid an accident.

3. AIRBAG WARNING LIGHT

Airbags have been almost an industry-wide fitment in European cars since the late 1990s. They are a key factor in mitigating occupant injuries in the event an accident takes place and this little logo means there’s something wrong with your airbag. Therefore, get to your nearest dealer or mechanic as soon as you can, and have the airbags checked out.

4. BATTERY WARNING LIGHT

This symbol indicates a low battery level or a problem with the car’s key electrical systems. You will see this illuminate every time you switch the car’s ignition on, but it should go out after a few seconds – and it should definitely extinguish once the engine is running. If it stays on, you may need a new battery or a full check of your vehicle’s electrics. And this is a serious one, because if the car’s electrical system fails while you’re driving, you could lose features like power assistance for the steering or electrical servo assistance for the brakes. Do not ignore it.

5. BRAKES WARNING LIGHT

This can manifest in a red symbol or a yellow one, and instead of the exclamation mark in the middle it might have the letters ‘ABS’. But it will always be a circle framed by two brackets like this, these brackets either being solid or rendered in three curved dashes either side. And, as you can imagine, faults with your brakes are of the most serious kind – as soon as you see this, you should slow down to a very low speed and head to the nearest garage immediately, to find out what is wrong.

6. COOLANT WARNING LIGHT

Traditional engines run on combustion, which simply means burning a fossil fuel. And burning means heat; quite a lot of heat. Thus, combustion engines need cooling systems and on all modern cars and almost all cars throughout history (there are some air-cooled exceptions, like older Porsche 911s and classic Volkswagen Beetles), the cooling is handled by a liquid-fed system. This coolant is a mix of antifreeze and distilled water, and if this little symbol pops up then you may not have enough coolant in the system to satisfy the engine’s requirements. It might be that you simply need to top your coolant up, which will cost a mere couple of Euro and only a few minutes of your time, or it might be that there’s a leak in the coolant system that you’ll need to have checked out. But the cost of sorting this is as nothing to what will happen if your engine cooks itself because it is running too hot, as a result of low coolant…

7. DIESEL PARTICULATE FILTER CLOGGED/FAULTY

We’ve talked about DPFs many a time in our Ask Carzone section. These are another item fitted to modern turbodiesels to meet emissions regulations, and the DPF is fitted in the exhaust. If you do lots of low-mileage, short-journey driving in which the engine doesn’t often get up to operating temperature, your DPF will clog up sooner rather than later, and this kind of logo will pop up on your dash.

8. DOOR/BONNET/BOOT OPEN WARNING

A fairly straightforward one, this; it means one or more of the car’s main apertures – the doors into the passenger compartment, the boot lid or the bonnet – isn’t closed properly. Simple fix: get out and check which thing isn’t firmly shut, and close it fully. More modern cars have even more advanced graphics that will show you precisely which door is open and even to what degree it is ajar, while an audible warning is often sounded to alert the driver that the car isn’t fully secure before moving off.

9. DRIVER ALERT WARNING

This will look slightly different from car make to car make, but in essence it always involves a ‘cup of coffee’ graphic. The driver alert feature is a safety system on modern cars that monitors steering inputs and throttle control, in order to work out when it thinks the driver is showing signs of fatigue or tiredness. If the system senses you’re driving erratically, this logo will pop up and the car will prompt you (often with a worded message, as well as the icon) to take a break. Sometimes, these systems are timed, so (for example) driving for three hours or more will trigger the coffee-cup warning, even if you’re controlling the car perfectly.

     

10. ENGINE WARNING LIGHT

Ah. The biggie. While no warning light on your car’s dashboard should be ignored for too long, if this one pops up you could have serious issues that you should attend to immediately. It can illuminate in either yellow or red, but either one means there is some sort of fault with the biggest component in your car: its engine (or, at the very least, the ECU controlling it). Now, to offer you some solace, sometimes the engine warning light can flash up when it’s a relatively minor issue, like a sensor fault or so on, but it is always, always, ALWAYS advisable to take your car straight to your nearest repair garage or main dealer to have it checked out. Ignore this and run the engine with a serious fault on it, and you could be looking at a repair bill in the thousands of Euro – or even your car being written off as uneconomical to repair.

11. FUEL WARNING LIGHT

Fairly simple, this one, and if you don’t know what it is by now then we’re guessing you’ve found yourself stranded by the side of the road more often than you’d care to mention. This fuel pump symbol means your car is getting low on either petrol or diesel (delete as applicable); go to a fuel station and fill up – ON THE CORRECT FUEL FOR YOUR CAR! Putting petrol into a diesel-powered vehicle is terminal to its health, so check very carefully which pump you are placing in your fuel tank nozzle filler come refill time. It’s not an absolute law industry-wide, but most fuel warning lights tend to illuminate when your car has around 80km of fuel range remaining until it comes to a complete, sputtering halt.

12. GLOWPLUG WARNING LIGHT

If you’ve got a petrol car, you can skip this one, as it only applies to diesels. Like the battery symbol mentioned above, this yellow, coiled glowplug symbol will come on every time you switch on the ignition of your diesel car. If it’s cold outside, it will stay on for slightly longer than if it’s warm or if the engine has been recently run. And here’s a top tip that not many people tell you: which is, you shouldn’t actually fire your diesel into life until this symbol has illuminated and then gone out again – glowplugs help diesel engines start from cold without any damage. If this symbol comes on while your diesel engine is running, there’s a fault with the glowplugs and you’ll need to get them checked out immediately, otherwise you might find your car won’t start, the next time you come to drive it.

13. ICY ROADS/COLD OUTSIDE TEMPERATURE

Does what it says on the tin, this one. It might illuminate yellow, it might illuminate red, it very often illuminates blue (and the car should make an audible warning noise too, when this comes on), but it is always a little snowflake graphic like this. Typically, it means the outside temperature is no higher than three or four degrees Centigrade, and therefore there’s a high chance of ice on the road surfaces – so go steady!

14. LANE DEPARTURE WARNING

Another relatively modern active safety system and one which, like AEB, goes under many names. But if your car is fitted with some type of LDW technology, then this little logo will illuminate when you’re straying out of your driving lane without having activated your indicators. It aims to stop you hitting other cars on the motorway or on dual carriageways through inattentiveness. If you’ve got the evolved version of this technology, which is often called lane keep assist (LKA), then your car will automatically steer you back into the middle of your lane if needs be.

15. OIL LEVEL WARNING

Two more biggies coming up. The first is this one, which suggests your car is running low on oil. Oil is absolutely vital to the lubrication of your engine – combustion engines use lots of moving metal parts in their innards, and without oil then you begin to get metal grating on metal; not good, and potentially terminal for your engine and/or your bank balance. If you see this show up in your dash, stop, buy some of the right grade of oil for your car (this will be listed in the owner’s handbook) and top it up as needs be. All cars should have a dipstick in the engine bay to allow you to regularly check the oil and prevent this light ever coming on in the first place.

16. POWER STEERING (PAS) FAULT

Like the engine warning light, the low oil lamp or the faulty brakes symbol, this is one not to ignore and one that you should get sorted ASAP. If your power steering fails, the car’s steering is suddenly going to be very heavy to operate, which might mean you can’t put in the right steering inputs and you could have an accident. It will normally illuminate because you’ve run low on power steering fluid, in cars with a hydraulic system, and so you’ll need some more of that fluid (bought from a good garage or a main dealer) to replenish the PAS. However, electromechanical steering has become all the rage these days, so if you’ve got a circa-2015-onwards car, this light becomes rather more serious, as it’ll likely need a senior technician’s know-how to sort out the issue.

17. RADAR CRUISE FAULT

Radar cruise, or Adaptive Cruise Control (ACC), is a system that allows a driver to set a given speed – say, 120km/h – for motorway driving. Once the car is up to 120km/h, it will then hold that speed and scan the road ahead, using camera and radar systems. If it senses a slower-moving car in its lane ahead and no effort by you, the driver, to overtake the car, it will then automatically slow down to hold a safe distance (which you can pre-set within the car) and also match the speed of the car ahead, until such time as the car moves out of your way or you overtake it – at which point your vehicle will automatically return to 120km/h. If this system is faulty and this symbol is showing on the dash, your car will not make any efforts to match its speed to the car in front and you could end up going up the back of said vehicle if you’re not careful. Therefore, get the radar/ACC checked out if you see this warning symbol come on.

18. SEATBELT WARNING

Like the low fuel light, this is one you really should know by now – even if you aren’t a driver. This denotes that someone in the car isn’t wearing their seatbelt, so get them to buckle up. Modern cars often have a graphic refined enough to tell you precisely which passenger hasn’t clunk-clicked their belt into place, as well.

19. TYRE PRESSURE MONITORING SYSTEM (TPMS) WARNING

We’ve saved the best until last. Or rather, we’ve saved the most infuriating until last. This is one that portrays a very serious fault – a loss of pressure in one or more of your vehicle’s tyres – but it can often be ‘the safety system that cried wolf’. As in, from our experience, this light coming on is often a ‘false’ reading: you’ll get the TPMS logo come up, you’ll creep off to the nearest air inflation device at any good fuel station, you’ll check all the tyre pressures… and they’ll be absolutely fine. Hence why we find it infuriating. But, unlike the village folk in the classic fable of the boy who cried wolf, regretfully you shouldn’t ever ignore TPMS, no matter how many times it has told you a pack of lies about your tyre pressures, because one of these days it’s going to actually pick up on a puncture or a loss of pressure… and you don’t want to fail to heed its advice in those circumstances.