Dashboard warning lights are just like your doctor – when they tell you something, you're wise to act on the advice.
So, when you start your car and all of the lights go out, you can move along – there's nothing to see here. But if one or two of the dashboard warning lights stay illuminated then it pays to know what they are and what they're telling you.
Ignoring the fact that optional equipment (and the associated warning lights) varies from one car to another, there’s a core set of warning lights that are common to most modern vehicles. Some are gentle reminders of things you'll need to attend to in time, some are merely for information, and some are so serious that you should pull over and shut off the motor as soon as it is safe.
Do you know which is which, and what they all mean? To give you a steer, we’ve broken them down into sections so that you know just what you’re dealing with – and what you need to do next when one lights up!
Stop the car!
Dashboard warning lights get no more serious than these. You or your car are at serious risk, and you should pull over and shut off the engine as soon as it’s safe to do so. Depending on the issue, some of these lights may indicate you need to call a tow truck or roadside assistance, because even if possible continuing to drive would be dangerous.
Check Engine Light (CEL)/Malfunction Indicator Light (MIL)
With the introduction of the OBDII system (onboard diagnostics, version 2) this light appeared in every car and on some motorcycles. If it is flashing it indicates a serious problem and you should pull over and turn off the car as soon as it is safe. When it lights up, it means the computer electronic control unit (ECU) has detected a problem in the engine or emission controls systems. The problem could be mechanical, or electronic, or could even be nothing more than a sensor going bad; you won't be able to tell without a code reader, but you should stop as soon as possible to investigate.
This indicates an issue with the brakes or the anti-lock braking system (ABS), and driving while the brakes are compromised is more than a little unwise. If it is an ABS issue, the car may be able to be driven, but you lose the added safety of ABS in a panic stop, and if it is a bad ABS sensor, you may lose stability and traction control as well. The brake light may also light up if your car has lost some brake fluid, or if the emergency brake has been left engaged.
Power steering failure
Modern cars use power steering, with either electric or hydraulic assistance, or sometimes both. Either way, if it calls it a day, not only will the dashboard warning light illuminate, but you'll be more than aware of the issue because the steering will suddenly become very heavy indeed. Without power steering a car can still be driven safely, but it will take considerable strength to steer; emergency maneuvers might be affected.
This warning light indicates a fault with the airbag system, also known as the supplemental restraint system (SRS). It doesn't affect the way the car drives or handles but could be very serious if you are involved in an accident. Driving with extra caution is suggested, but you should be safe to continue on to home or work. A variation of this light could light to indicate the passenger side air bag has been deactivated, manually or because a baby seat is detected.
This old-style oil fill jug warning light indicates that something in the engine oil is below optimal. Similar lights can mean oil pressure, oil level (an oil jug with a wavy line below it), or oil temperature (with a thermometer). When this light is red it means that there is not enough oil pressure in the engine to circulate the oil and prevent wear. You must pull over and shut off the car immediately or the engine could be damaged. If the light glows amber, it is less serious, but still means you need to check and possibly add oil as soon as possible.
Typically when this dashboard warning light glows red it means your car is getting close to overheating, and you risk causing serious damage if you continue to drive. If this light comes on red soon after starting the engine, it likely indicates the coolant level is low. Some cars illuminate the same light in blue when the car is cold to remind you to drive less aggressively until the engine is fully warm.
If one or more doors are not properly latched, you should stop and fix it as some as it is safe to do so.
Slightly less dangerous than a door being unlatched, the hood or trunk/hatch coming open while driving is still a safety issue. Most modern cars will now warn you before a dangerous situation happens, like an unlatched hood flipping up and blocking your view of the road.
Not every warning indicator on the dashboard is something serious that you ought to be concerned about. Many are just reminders to perform ordinary maintenance tasks.
General service reminder
The computers in cars today keep track of general driving conditions, and mileage, to be able to remind you to have your car serviced periodically. Often an amber or red wrench will appear, or the words "service engine soon", to let you know that it is time for an oil change or other service. Which service and how frequently differs by make and model, and if you follow our accelerated service plan you will find yourself resetting this light frequently before it is even activated.
Tire Pressure Monitor System (TPMS)
Tires lose air over time, and the pressure can also be affected by a drop in ambient temperature, which can affect handling, braking, and fuel economy. For these reasons many modern cars have small electronic monitors in the wheels that will warn you on the dash if a tire is off by as little as 5 psi. Typically this isn't cause for alarm, but a TPMS light can indicate that you have run over something and a flat is imminent, so it's worth pulling over to check.
Loose gas cap
Modern emissions are so strict that the fumes evaporating out of an open gas cap can contain several times more unburned hydrocarbons that what comes out the tailpipe. For this reason cars now have sealed systems, and will alert you if a leak is detected. Typically, it's just a case of undoing the filler cap and screwing it back in until it clicks.
Low fuel warning
Most of us keep a pretty sharp eye on the fuel gauge, but the fuel warning light is a useful reminder that you’re on borrowed time. Depending on your car you may have 15-30 miles worth of fuel in the tank – your car’s owner's manual may tell you how much range you have left before you have to get out and push, or many cars these days will start counting down estimated range when the light comes on.
Diesel exhaust fluid (DEF)
Plenty of diesel pick-ups are sold in North America, and they have their own specific dashboard warning lights, the most important of which is the DEF light. DEF is the blue fluid injected into diesel exhaust to fight pollution, and if you run out your truck will go into limp mode or may not start. When this light is lit, fill up the blue diesel exhaust fluid tank at the next fill up.
Key fob missing/battery low
With proximity keys, you no longer have to insert the key into the slot to start the car, but you do need a key with a good battery in it. If the battery goes dead you may not be able to start the car, or you may be forced to use the manual back-up. Your car should give you plenty of warning before that happens, with a warning light on the dashboard. This light will also warn you if you try to drive it without the key, if for instance, the passenger gets out and takes the keys with them. Unfortunately, many cars will allow you to drive for miles before immobilizing themselves, stranding you miles from the keys.
On cars with daytime running lights (DRL), it can be hard to tell if your actual headlights are on. This can be dangerous because the DRLs are not as bright as the headlights. To counter this, most cars now have a green lantern shape to indicate your lights are on, or sometimes an indication that they are on "auto". This can look similar to the high beam indicator, but is green instead of blue.
A washer fluid warning light? Believe us, it's important. Washer fluid is more important than it seems, as anyone who has suddenly found themselves driving into the setting sun with a dirty windshield can attest to. You can go days and weeks without using the windshield washer, so it’s easy to be surprised when the reservoir needs filling up. A washer fluid warning light avoids this.
These are some other warnings you might see, but typically they mean you have a problem, not the car.
Parking brake on
As mentioned earlier, if you leave the parking brake on you will get a warning, long before the smell of burning brakes alerts you. This may be a red circle with a "P" in the middle, or it could just be a multi-purpose brake warning indicator. There's ususally an audible warning to accompany the light.
This needs no explanation, we all know we should buckle up for safety, and if you don't your car will remind you with a light and a beeping alarm.
As for the rest…
We couldn’t include every single warning lamp on every single car model, so we’ve stuck to the really important ones that could make the difference between dangerous driving, expensive repairs or a ticket from law enforcement officers.
You have been warned. (Ahem.)