Vehicle's Warning Lights & Indicators: What Your Car Is Trying To Tell You

Every driver experiences a mechanical failure at some time or another, even when their vehicle is new and well-maintained. Fortunately, most modern vehicles are built with a warning system which indicates when an important component has malfunctioned or is at risk of failing. If this happens, a warning light will usually be triggered on the dashboard to tell the driver that some action is required.

Refer to your owner’s manual

In this module, you will learn to recognize and respond to vehicle warning lights. However, you must read your vehicle owner’s manual thoroughly too. The information we provide is widely applicable and relates to most vehicles, though it may not cover all vehicle-specific warning lights and operating systems.

Check engine light

When illuminated, the "check engine" light indicates that something is wrong with the engine. Sometimes, this warning light can be triggered by something as simple as a loose gas cap – so there is no need to panic if you see it lighting up. That being said, you should never ignore a check engine warning light, as it may also indicate a more dangerous malfunction, such as problems with the catalytic converter or ignition system.

If you do not have the expertise to give your engine a thorough health-check yourself, drive it to a qualified mechanic as soon as possible. They will be able to identify the cause of the warning light and rectify the problem for you. Keep in mind that minor problems will often become more severe if left unattended. Failure to get your engine checked out right away could lead to greater expense and inconvenience in the long-run.

Oil pressure light

Your oil pressure light will come on if the oil pressure in the engine is too low or too high. Both causes can result in serious damage to your engine, so you will need to investigate this warning light as soon as possible. If the problem is low pressure and you have extra oil in your car, you should be able to resolve the situation and get back on the road in a few minutes.

When pulling over to check your oil, be sure to park on a flat surface. Stopping your car on an incline will stop you from getting a true oil-level reading. Remember to wait a few minutes after pulling over to let your oil settle before checking it. The follow these instructions:

1. 1

   First up, you will need to locate the dipstick.
   They are usually topped with a brightly colored metal or plastic ring which serves as a handle. When you have removed the dipstick from its holding shaft, use a tissue or rag to wipe it down.

2. 2

   Re-insert the dipstick all the way into the shaft and hold it there for a few seconds, before removing it again to check the oil level.
   If the level is too low, the mark left by the oil will end below the lowest marker on the dipstick. If this is the case, add another quart of oil to the engine.

3. 3

   If the level of oil is too high, your oil pressure light is on despite a normal reading or if the oil appears to be contaminated with dirt, sludge, bubbles or another residue, you will need to get a mechanic to check out your engine.

Battery warning light

Never ignore your car’s battery warning light. Every electronic system in your car is run by your car battery – including ignition. If the battery runs completely flat, your car will be dead in the water. Car batteries are designed to recharge automatically while you drive, though various mechanical issues can prevent this from happening efficiently. The most common cause is the alternator belt being too tight or too loose, though complete failure of the alternator is another possible issue.

The battery warning light indicates a charging problem with the battery. Your car may continue to run for a short time, as it is can utilize power stored in the battery. However, nothing in the vehicle will work as soon as that power is used up. If your battery warning light comes on, you should switch off all non-vital electrical systems to preserve your remaining power and make your way to a mechanic immediately. Allowing the battery to run flat could stall your engine and cause damage to the vehicle.

You may find that switching off electrical components in your vehicle deactivates the battery warning light. If the light comes back on when you re-start these components, your battery still needs to be checked out by a mechanic. The fact that it temporarily turned off simply means there was less strain on the battery’s power supply at that time.

If you are in a situation where the battery warning light is active and the engine will not turn on, it is likely you will need to jump-start the car to get it going again.

Engine temperature gauge

A vehicle’s internal combustion engine ignites fuel to create thermal energy, which is then transformed into mechanical energy to power the wheels. A great deal of surplus heat is produced during this process, which would cause engine components to overheat and fail were it not for your engine’s cooling system. Coolant has an extremely high boiling point and can absorb heat from the engine. If your engine temperature gauge is in the red or the temperature warning light activates, the cooling system is failing to keep up with the heat given off by the engine.

An overheating engine could be caused by an internal issue, such as insufficient coolant. It can also be caused by outside factors, such as excessively hot weather or the strain which sitting in stop-and-go traffic places on the engine. When the engine temperature gauge or warning light indicates that your engine is too hot, you should turn off systems that place strain on the engine (such as air conditioning), pull over at the next opportunity, turn off the car, pop the hood and let the engine cool down. If possible, pick a spot in the shade.

If it is not possible to pull over right away, you can help your engine cool down by turning the air temperature up to high and air speed up to maximum. This will vent hot air from the engine into the car. Rear-wheel and four-wheel drive vehicles often have belt-driven radiator fans (find out in your vehicle owner’s manual). Such vehicles can be cooled slightly by shifting the car into neutral and applying light pressure to the accelerator.

Check your coolant levels when you have successfully pulled over but wait for the engine to cool down first. Opening the radiator or coolant tank when the engine is still hot could cause an eruption of boiling coolant. Top up the tank with coolant if levels are running low. As a temporary solution, if you do not have more coolant, water can be added to the radiator. Note that this must not be used as a long-term resolution.

Brake warning light

If your brake warning light comes on, begin by checking if your parking brake is set and deactivate it if that is the case. This is one of two reasons your brake warning light may be illuminated. The second and more serious cause is low or non-existent brake fluid pressure.

When the brake warning light is active while you are driving and the parking brake is evidently not the cause, test your brakes by pressing down onto the pedal lightly. Do not panic if there is little or no response from the brakes, you can pump the brake lightly to try and build up some pressure. If this does not work, you can gently apply your parking brake to slow down and pull over.

You must get a mechanic to check over your vehicle immediately if the brake warning light has come on, even if there is only a slight loss of response in the brakes. A more dangerous issue may develop if you do not act. Next time you drive, you may experience total brake failure.

ABS warning light

If your vehicle is equipped with an antilock braking system (ABS) make sure you know where the ABS warning light is located on the dashboard. An active ABS warning light indicates that the ABS system is malfunctioning. Get a mechanic to look at your car as soon as possible.

You may continue driving with a malfunctioning ABS system, though you must be prepared to prevent skids manually while braking. This will mean applying the brakes earlier and more gently than you would with ABS. Pressing down too hard could cause your wheels to lock up – pump the brake pedal to release them if this happens.

Airbag warning light

When active, the airbag warning light indicates that the airbags are malfunctioning in some way. This is usually because they have been deployed previously and reset incorrectly. It is important to have a mechanic investigate the airbag issue as soon as possible, as your airbags may not work properly during a collision.

Tire pressure warning

The tire pressure warning light will come on when the air pressure in the tires is low. With insufficient pressure, your tires will be more susceptible to blowing out and your ability to control the vehicle may be affected. Low pressure can be caused by general wear if your tires are coming toward the end of their lifespan, a puncture, a slow leak or cold weather.

Pull over and check your tire pressure at the next safe opportunity if your tire pressure warning light is active. If any of your tires are flat or nearly flat, you will need to call for assistance to either replace or repair the tire by the roadside. Otherwise, you can drive to the nearest service station to top up the air in your tires.

Use the air machine to fill each tire to the vehicle manufacturer's recommended tire pressure. You can usually find this information printed on the inside of the driver’s door jamb. Ignore any pressure specified on the tires themselves – this is the highest pressure the tires can take without rupturing and has no relation to the tire pressure your vehicle requires. Always pump your tires to the car manufacturer's specifications, as this will be the ideal pressure to provide good traction and fuel economy while maximizing the lifespan of the tires.

However, remember that a 10°F increase or decrease in outside air temperature will cause tire air pressure to rise or drop by 1 psi respectively. You will need to compensate for this in particularly cold or hot weather.

Open door warning light

Modern vehicles are built with open door warning lights, as an improperly closed door can be incredibly dangerous. In the event of a crash, a person may be thrown from the vehicle or insufficiently protected if the car door is open. There is also the risk that the door may swing open and strike other traffic while the car is in motion. The open door warning light may also be referring to an open trunk, which can prevent you from seeing behind your vehicle while driving.

Do not test your doors while the vehicle is in motion if the door warning light comes on. Instead, pull over to a safe spot to check that all doors are properly closed. If the open door warning light remains on, get your car looked at by a mechanic. This could indicate a mechanical malfunction with a door or the trunk.

Low fuel warning light

The low fuel warning light indicates that your fuel tank is at risk of running empty. Different makes and models of vehicles have different activation points for the low fuel warning light. In some cars, the low fuel light may come on when you have two gallons or less left, in other cars, this may only occur at one gallon or less.

You should make your way to the nearest gas station when this warning light comes on, or better yet, top-up your fuel before it gets too low to avoid this problem altogether. When your low fuel warning light is active you can conserve fuel by accelerating gently and letting the vehicle coast as much as possible.