What does that car warning light mean?
Start your car engine and a variety of dashboard lights will come on and, after a few seconds, go off again… except that sometimes they don’t.
Many car warning lights are common to all manufacturers: the oil can warning light; the engine warning light; an ABS warning light... some of them are gentle reminders of things you need to attend to, some of them are there for information only and some are extremely serious and you have to act straight away.
How do I reset a car warning light?
AutoFix from Haynes is the most advanced car repair tool you can buy, and features a section on car warning lights that tells you what the light means and what you need to do to make it go away.
Car warning lights explained
So which is which, and do you really know what they all mean? The image below shows most of the warning lights you'll find on your dashboard – below that we explain what they mean and what you need to do.
Which warning lights should I stop the car for?
These warning lights are shown under STOP THE CAR! in the picture above.
You or your car are at serious risk, and you should pull over and turn off the engine as soon as it’s safe to do so and get some help from a roadside assistance service or a local garage.
Engine warning light
This indicates a mechanical fault with the engine, or a problem with the ECU, the electronic Engine Control Unit. The engine may fail (expensive and potentially dangerous) or it may enter a limp-home mode that will get you to a place of safety but no more.
Brake warning light
This indicates a fault with the braking system, and the consequences hardly need spelling out. At the very least you may lose servo assistance, making the brakes extremely heavy to operate, and at worst the brakes could fail completely. An ABS lamp indicates the Automatic Braking System has a fault, making skidding under braking more likely.
Steering warning light
Practically all modern cars use power steering, and if this fails the steering will become extremely heavy, so that it’s difficult or impossible to control the car safely. You may be able to manoeuvre it to a safe position at low speeds, with effort, but it will be dangerous to drive at normal speeds.
Airbag warning light
This indicates a fault with the airbag system, which does not affect the way the car drives or handles but has very serious consequences – obviously – if you are involved in an accident. Airbags are an integral and essential part of the car’s safety system, and they are not just an optional extra.
Oil can warning light
On some cars this may glow amber to indicate a low oil level, but generally this is a red warning lamp indicating a serious loss of oil pressure. This could be due to insufficient oil or a more serious mechanical failure. If you keep driving, the engine is likely to fail completely, suffering serious damage in the process.
Cooling system warning light
This lamp indicates that there’s too little engine coolant or that it’s exceeded its maximum temperature. If you carry on driving, the engine will overheat, its performance will suffer and it may stop entirely, quite possibly with serious damage.
What about routine maintenance car warning lights?
If you do your own maintenance you should be on top of all these little jobs, but just in case you might forget, your car will eventually remind you about these everyday essentials you might have overlooked.
All of these are shown under the ROUTINE MAINTENANCE section of the picture above.
Oil level warning light
This is often the same oil can symbol used for the oil pressure warning, but this time glowing or flashing amber to indicate that the situation is not yet urgent but this is something you do need to attend to promptly.
Washer fluid warning light
You can go days or weeks without using the windscreen washers, so it’s easy to forget that reservoir needs to be refilled. Washer fluid is more important than it sounds. If you’ve ever run out of washer fluid on a greasy motorway while overtaking a juggernaut, you’ll know why.
Fuel warning light
Most of us keep a pretty sharp eye on the fuel gauge, but now and again we’re distracted and forget – or we’re just putting off that boring trip to the petrol station. The fuel warning light is a useful reminder you’re on borrowed time – your car’s manual or dash computer will tell you how much range you have left.
Tyre pressure monitor warning light
If your car is a few years old you might not have seen this, but it’s become a standard fixture on new cars and it’s very useful. Tyres lose pressure so slowly you may not notice, but underinflation increases tyre wear, reduces fuel efficiency and can affect the car’s handling.
Brake wear warning light
Many cars also have a brake wear indicator. If you check your car regularly you’ll know when the brake pads need to be replaced; otherwise this warning lamp will tell you. The consequences of leaving the pads to wear out completely hardly need explaining.
Diesel particulate filter warning light
Modern diesel engines create a lot of particulate emissions during slow-speed running and these are collected by the particulate filter. This ‘soot’ is burned off automatically during higher-speed running, so the filter normally takes care of itself. This warning light indicates your car needs some A-road driving to clear the filter. Don’t leave it too long or the filter could eventually become blocked, which is more serious.
Glow plug warning light
Glow plugs are small, fast-acting heating elements that fit inside the cylinder and help diesel engines with cold starts. Most of the time you can forget they are there, but if you see this lamp you need to get them checked out and/or replaced. If you don’t, your engine may not start reliably, or it may not start at all.
Oops! warning lights
This section is for those car warning lights that tell you when you just did something dumb. You just need to stop the car, sort it out and hope no one noticed.
Parking brake left on
The car didn’t pull away very well, did it? And you’ve also got some kind of annoying beeping sound – and this warning lamp on the dash. The clues are all there – you didn’t release the handbrake properly. In fairness, on some cars it’s easy to accidentally not push the lever all the way down.
Seat belts not done up
Rules are rules. You might only be driving down to the corner shop to buy some milk, but you still need to put on your seat belt. More seriously, this is a handy reminder when your passenger decides not to bother, too, or if an elderly relative can’t find the buckle and is only pretending to wear the belt. Yes, we’ve all been there with that one.
You’re in a rush, you didn’t latch the door properly and now it’s rattling about as you drive along. All doors have a secondary catch to stop them flying open, but you still need to stop and fix it. Do NOT try to lean across to open and close the door while you’re driving. Did we really need to say that?
You’ve done the oil (check), you’ve done the coolant level (check), you’ve filled the washer reservoir (check), but you didn’t shut the bonnet properly (uncheck). The catch should stop it flying open as you drive along, but when the wind gets under it, it will try very hard to lift it.
You may already know the boot is open because you’ve crammed it with 15 percent more stuff than the car was every designed to carry. Otherwise, this is a handy warning that you haven’t shut it properly, and that it’s going to be rattling around behind you until you do.
Learn those lights
We all know what our lights are for and which to use when, don’t we? Sure we do. But in a strange car, or unusual conditions, it’s still possible to get confused. Here’s a quick rundown, including a couple that we reckon a lot of people can still get wrong.
Drivers of a certain generation may still call these ‘sidelights’ and still use them for driving around at dusk. Wrong! They’re parking lights for use when the car is stationary on an unlit or poorly lit road. When you’re driving, use dipped or main beam headlights.
Use these when you face oncoming traffic so that you don’t blind other drivers. The dipped beam lamp is green and has the light ‘rays’ angled downwards to show that they’re aimed at the road surface ahead.
Only use these when there’s no risk of blinding oncoming drivers, and remember that the lamp for this is blue not green, so when you’re driving at night that blue glow from the dash is your reminder to dip the lights as soon as you see someone coming the other way.
This is too easy. These left and right-facing green arrows show that the car’s turn signals are activated. On some cars, though, they both light up, not one or the other, so it’s a generic warning and doesn’t tell you which way you flicked the switch. But you probably ought to know that anyway.
Front fog lamp
The switches and lamps for the front and rear fog lights look quite similar. In fact, the front fog lamp symbol faces to the left, the ‘rays’ are angled downwards and a wavy vertical line indicates the ‘fog’.
Rear fog lamp
The rear fog lamp faces to the right and the ‘rays’ are usually horizontal – again, a wavy vertical line indicates the ‘fog’. Do NOT leave your front and rear fog lights on because they look good or just to be ‘on the safe side’. They dazzle other drivers and the law is clear – you MUST switch them off as soon as visibility improves. So there.