As cars have become more complex, the number of different dashboad warning lights has grown significantly. Modern electronic systems like airbags or stability control are constantly self-testing and it’s important for you to know whether a warning light requires immediate attention or whether you can continue your journey and get a garage to investigate later.
If a warning light comes on (or fails to extinguish after you’ve started the engine) you should stop as soon as possible in a safe place.
Many warning lights are specific to the car make or even the model – the vehicle handbook should give you a detailed explanation of their meaning and the action to take.
Oil pressure warning light
Just like your car’s water or coolant warning light, you might see an oil warning light flash up if oil temperature gets too high, the level is low or oil pressure too low. It’s the latter two you want to avoid at all costs.
Oil is what lubricates your engine, with the oil pump used to spray the fluid to all corners of your engine. If temperatures get too high, or even worse, level is low or oil pressure drops, the effectiveness of the lubrication can be reduced or lost all together
The result? Expensive engine damage, so if you see this warning sign, stop and phone a professional right away.
Battery charge warning light
If it does not illuminate at all, or if it illuminates while driving, your battery is not being charged as there is a fault with your charging system.
This may be due to one of the following;
- slack battery or starter terminal
- a broken or loose alternator drive belt
- an alternator failure
If the drive belt is broken, it must be replaced before you restart the engine. The coolant system may rely on this belt and its failure could cause the engine to overheat, in turn causing engine damage.
Immediately move the vehicle to a safe location and switch off the engine. Do not restart the engine and seek assistance.
Brake system warning light
Refer the the handbook and add the correct brake fluid at once to bring the level up to the MAX mark. As the brakes wear the fluid level will slowly drop. Check your brake fluid level frequently to ensure there is no further rapid loss of fluid.
If the brake fluid is too low and brake pedal travel is distinctly longer than usual, one of the two hydraulic brake circuits may have failed. Do not continue your journey and seek assistance.
If the light remains illuminated, even though the brake fluid level is correct, this may indicate a sensor fault. Take your vehicle to a dealer or garage as soon as possible.
Diesel Particulate Filter (DPF) partially blocked
As with any filter (think of the bag in your vacuum cleaner) they have to be emptied regularly to maintain performance. For a DPF this process is called ‘regeneration’ – the accumulated soot is burnt off at high temperature to leave only a tiny ash residue. Regeneration may be either passive or active.
Passive regeneration takes place automatically on motorway-type runs when the exhaust temperature is high. Many cars don’t get this sort of use though so manufacturers have to design-in ‘active’ regeneration where the engine management computer (ECU) takes control of the process.
When the soot loading in the filter reaches a set limit (about 45%) the ECU can make small adjustments to the fuel injection timing to increase the exhaust temperature and initiate regeneration. If the journey’s a bit stop/start the regeneration may not complete and the warning light will illuminate to show that the DPF is partially blocked.
It should be possible to start a complete regeneration and clear the warning light by driving for 10 minutes or so at speeds greater than 40mph.
Engine warning light
If it illuminates with the engine running, it indicates a malfunction with the engine management system. Have this checked as soon as possible.
If it flashes when driving, reduce the vehicle speed immediately until the light illuminates constantly. If it continues to flash, avoid heavy acceleration and high engine speed, stop the vehicle and have it checked immediately.
On some vehicles this light may be red – again stop the vehicle and seek assistance.
If it is safe to do so, try stopping the vehicle, switching off the engine, wait two minutes, then restarting the engine to reset the engine management system.
With the light illuminated, the vehicle is still safe to drive as long as no other faults are apparent with the engine. Have the vehicle checked by a dealer or garage as soon as possible to avoid any damage being caused to the catalytic converter.
ABS warning light
If it illuminates when driving, it indicates a malfunction. Have this checked as soon as possible.
Normal braking (without ABS) will be generally be maintained and many cars will be safe to drive on, but some will not – check the handbook for advice.
Have the vehicle checked by a dealer or garage as soon as possible.
Brake system and ABS warning lights
Reduce vehicle speed gradually and immediately move the vehicle to a safe location. Use the brakes with great care. Do not step on the brake pedal abruptly. Seek assistance.
Fuel filter water trap (diesel engines)
This light illuminates when the ignition is switched on and should extinguish after a few seconds.
If it illuminates while driving, it indicates that water has been detected in the fuel filter.
This light warns you that the amount of accumulated water in the fuel filter has reached the specified level.
Normally the vehicle is quite safe to drive, but have the accumulated water in the fuel filter drained off as soon as possible.
If the vehicle has just been re-fuelled, immediately move the vehicle to a safe location and switch off the engine. The fuel may have been contaminated and could cause damage to the injection system.
Airbag warning light
A faulty airbag potentially won’t go off in a crash, meaning you and your passengers won’t be as well protected from any potential injuries. The other possibility is that your vehicle’s airbag could deploy when you least expect it, giving you a nasty shock – or even actually causing an injury – and an expensive fix to put right.
Coolant warning light
Without any coolant, your car’s engine would get so hot it’d effectively ‘weld’ itself together. If you see the coolant light show up on your dashboard, it could mean coolant levels are running low, so check the gauge on the side of the coolant tank under the bonnet and top up if necessary.
In conjunction with a temperature gauge reading well into the red, it could mean your engine is overheating. This is either the sign of a larger problem – like a head gasket failure – or symptomatic of something less major, like a leak in the system somewhere, meaning you’re engine has run low on coolant and got too hot. Get it seen to as soon as possible to avoid a potentially expensive repair bill.
Tyre pressure monitor warning light
These systems can sense a deviation away from normal tyre pressures, signifying a puncture. Generally, the device will flash a warning light on the dashboard, highlighting you should take a look at your car’s rubber.