Cars are certainly getting smarter, but there aren’t many on sale today that can tell you what part of them is broken in plain English. Most cars still feature a series of warning lights on the dashboard which illuminate when the car’s ECU detects a problem with a component – and these lights are used to guide your mechanic to the issue.
These warning lights tend to cover large portions of your car’s mechanicals. There’s often just one lamp to inform you of any problem that occurs with your engine, for example – and the same can be said of the warning lamps for your car’s electrical and cooling systems.
Below, we’ve compiled a list of the most common dashboard warning lights and provided a brief overview of what each means. We also give an indication of the likely severity of the issue flagged by the warning light and outline the steps you need to take to fix the problem that illuminated the light. Spoiler alert – this normally means taking your car to a mechanic.
Engine management warning light
The engine management warning light is probably the most common warning you’ll see on your dashboard – and it’s every motorist’s nightmare. On its own, the lamp isn’t much help as it doesn’t tell you what’s wrong with the car. To narrow down the problem, you’ll need to take your motor to a mechanic with the correct diagnostics tool.
A diagnostics tool is a small computer that can read the computer that runs your car by connecting to a socket under the dashboard (called an OBD port). If there’s a fault, it’ll be attached to a code which the mechanic can check against a database – and that should lead him straight to the problem.
An engine management light doesn’t always mean there’s something catastrophically wrong with your car’s engine. This warning light illuminates for a variety of issues ranging from trivial gremlins such as a loose dipstick or a vacuum leak to more serious problems like a damaged oxygen sensor or clogged fuel injectors.
Generally, if the engine management light is solid the problem is minor and you can continue driving – but we recommend getting your vehicle checked as soon as possible. If the engine management light is flashing or red, pull over to the side of the road quickly. It could be indicating serious (and very expensive) problems with your vehicle.
Some classic cars feature a similar warning light, but it isn’t connected to any sort of diagnostics system that can tell a mechanic what’s wrong with the car. Instead, this light is designed to warn you of an imminent and very serious problem, such as low oil pressure, overheating or charging system problems.
Battery warning light
This one’s a little simpler than an engine management light. If the battery warning light comes on, it means your battery isn’t charging. A failed alternator is a common culprit, but it could be something more trivial such as a snapped alternator belt or a break in the wiring that runs your car’s charging system.
If the battery warning light illuminates, stop in a safe place and switch the vehicle off. Don’t try to drive any further, as you’ll probably end up damaging the battery. Running a car without a charging system for extended periods of time will draw too much voltage from the battery and prevent the cells from storing a charge.
That means you’ll need to pay for a new battery in addition to the fix for the fault with your charging system. Prices for a fresh car battery range between £50 and £150 depending on your car’s make and model – and that’s money you needn’t spend. However if you need a new battery, read our handy guide to find the best on the market.
Oil pressure warning light
Another fairly self-explanatory one. If this little oil can pops up on your dashboard as you’re driving along, it means your engine doesn’t have any oil pressure. You should stop your car immediately and check the engine oil level using the dipstick.
This plays out two ways. The first (and more favourable) scenario is that your dipstick shows that your engine oil level is low. In this case, you can simply fill your engine to the correct level with the correct oil, check that the light has extinguished and continue driving. Your owners manual will tell you which grade of oil to use and how much oil your engine needs.
The second scenario is more of a concern. If you check the dipstick and it’s showing you have the correct amount of oil in your engine, it could mean that the oil pump is broken or your oil filter is blocked. Don’t drive your car any further, as your engine won’t be properly lubricated – and that can cause some very serious and very expensive damage.
Brake warning light
This symbol appears on the dashboard when you have your handbrake (or electronic parking brake in the case of modern vehicles) engaged. However, it can also illuminate when there’s a problem with your braking system.
If this light is showing while you’re driving, make sure that you’ve fully released the handbrake first. If the handbrake isn’t engaged, check if your brakes feel spongy. If so, it could mean there’s a break in the hydraulic lines that connect your brake pedal to the brake callipers – and that means your brakes won’t work.
If your brakes feel normal, check the amount of hydraulic fluid in the brake reservoir under the bonnet. If the level hasn’t changed (there are lines on the bottle to tell you where the level should be), it could be just a sensor failure or a warning to let you know the brake pads need replacing. Drive to a mechanic as soon as possible to have the issue mended.
Anti-lock braking system warning light
This light lets you know that there’s a problem with your car’s anti-lock braking system. You should assume the worst and expect that your ABS is out for the count, so take extra care when driving in wet conditions. Avoid hammering on the brakes if you can, as your wheels will lock up – and this will increase your braking distance.
It’ll probably just be a failed sensor, but it’s worth taking the car to a mechanic and having the problem remedied. More worrying is when the brake warning light and ABS warning light are both illuminated, as this indicates a serious problem with your braking system. If you’re on the road, slow down gradually and phone for help. Do not drive the car any further.
Diesel particulate filter warning light
All modern diesel cars (and some modern petrol cars) are fitted with particulate filters in their exhaust systems, which trap harmful soot particles and convert them to harmless ash when the exhaust warms through. However, this doesn’t happen on short journeys – so you’ll probably see this light often if you’re only using your car for pottering around town.
Thankfully, it’s an easy fix. If you act on the warning light early, you can just take your car for a longer drive on a fast road. Getting the car up to temperature and taking it for a 30 minute drive up an A-road at sustained speed should be enough to clear the blockage.
However, if you ignore the light, the soot will continue to accumulate and your car will eventually enter a restricted performance mode. If this happens, you’ll need to take your car to a mechanic to have the DPF manually cleaned or replaced, neither of which are cheap.
There are some affordable DIY diesel particulate cleaners on the market, some of which have the added benefit of shifting the soot from components like your turbocharger and fuel injectors. However, they’ll struggle to shift serious DPF blockages.
Tyre pressure monitoring system
In the old days, you just had to “know” when you had a flat tyre by recognising a difference in the way the car handled. In the modern world, we have technology that communicates this problem to us – but it isn’t always the most reliable system, especially on more affordable vehicles.
For example, the previous-generation Ford Focus has a particularly sensitive tyre pressure monitoring system. The light can illuminate even when all of the car’s tyres are inflated to the correct pressure. We recently fell foul of this foible on a drive up north and spent two hours waiting for a recovery van, only to learn that there was nothing wrong with the tyres.
If you see this light on your dashboard, we recommend pulling over as soon as you can. Continuing to drive on a flat tyre is very dangerous, as you won’t have as much control over the vehicle, so check your tyre pressures and inflate as necessary. If there aren’t any leaks in your tyres, it should be safe to continue driving.
Monitor the situation carefully once you’re on the road again. If the light doesn’t switch off after a few miles, stop and check your tyres again. It could be that you have a slow leak which is tripping the sensor. If your tyres are fine, it’s possible that there’s a fault with the tyre pressure monitoring system, or that the sensors simply need to be reset.
Engine temperature warning light
If you see the engine temperature warning light on your dashboard, stop your car immediately. It means your engine is running far too hot. Continuing to drive will eventually result in your engine jettisoning its internals all over the road – and costing you thousands in repairs.
It could be something simple (and relatively inexpensive), like a burst radiator hose allowing the coolant to leak out of the radiator. Or, it could be something far more serious such as a blown head gasket. A tell-tale sign of the latter is white smoke belching from your exhaust.
Airbag warning light
This one’s easy to interpret. An airbag warning light informs you that there’s a fault with your car’s airbag system. So, if you have a crash, your airbags won’t deploy – and that means you and your passengers are at a far greater risk of injury.
If you see this light, we recommend taking your car to a mechanic as soon as you can. Hopefully, it’ll be something simple like a damaged wiring connection to the sensor under the seat or a loose item interfering with the seat belt sensor. Either way, it’s important you get it checked. It’s also worth knowing that an illuminated airbag warning light will make your car fail its MOT.
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