What the warning lights on your car dashboard mean and how serious they are
As you head towards a crucial meeting or important family event, an alarming warning light flashes on the dashboard.
It could be nothing, or it could be a nightmare in the making. Many of us don’t know how to tell the difference.
Because our cars have over 50 different warning symbols, you may be alerted for something as simple as the trunk not being closed properly, but you may also be alerted to an impending serious engine failure.
We enlisted the help of car diagnostic equipment expert Carly to help you understand what your dashboard lights mean and the potential cost implications of something bad.
It has reviewed 8.5 million diagnostic checks over the last six months and shared exclusive data with the Daily Mail and This is Money on the most frequently recorded fault codes that drive lights and the potential repair costs on the average car.
Below we explain their findings, what the warning lights mean, and what to look out for.
What you need to know about warning lights
The severity of a problem is indicated by the color of the dashboard symbol.
If you have an icon that glows green, white, or blue, you’re OK, as these lights are only shown on the dashboard to let the driver know that things are working properly or that a feature like high beam is in use.
However, if it is a yellow or red warning light, you may have more cause for concern.
The RAC says red usually indicates a potentially dangerous problem and drivers should stop the vehicle and have it checked by a qualified mechanic as soon as it is safe to do so.
Amber icons tend to highlight when something needs to be investigated, but it’s not that urgent.
Common mistakes and their costs
Engine management warning light: £64 – £2,400
Also known as the ‘check engine light’, this light glows amber or red depending on the severity of the problem and can be solid or flashing.
Carly says the faults that often trigger this can be as simple as an electrical problem with the oil cooling valve, and repairing a dodgy connector can cost as little as £64.
Problems with the ECU (the electronic control unit that acts as the brain of the car), catalytic converter and fuel pump also often cause this warning light to come on.
But the most important of the most common malfunctions is the lack of boost pressure of the turbocharger. Fixing a boost leak can cost as little as £134, but if the turbo needs to be replaced this usually costs between £1,300 and £2,400.
Airbag warning light: £139 – £2,160
When at least one element in the airbag system is malfunctioning, the airbag – or Supplemental Restraint System – symbol will illuminate red.
Carly says three of the 20 most common malfunctions that trigger the lights are related to the airbag ignition circuit, the electrical path that connects the control module to the airbag inflator.
If this is found to be a wiring fault the repair cost could be as little as £139. However, if the problem is sensor-related, it will cost between £540 and £768 to fix the problem. In a worst-case scenario, if the problem is caused by the airbag itself, replacement costs between £1,440 and £2,160.
Glow plug warning light: £134 – £1,504
Glow plugs are metal heating devices that are installed in the cylinders of a diesel engine and preheat the combustion chamber to ensure smooth engine operation. If the special glow plug warning light remains on after starting, this is usually a sign that the spark plugs need to be replaced.
Fixing a faulty glow plug can cost up to £1,504, but if the problem is caused by a faulty plug connection it could cost as little as £134.
Diesel particulate filter warning light: £150 – £2,610
The diesel particulate filter is designed to capture harmful pollutants before they can be emitted from a diesel car’s exhaust. However, over time, it can become clogged or clogged, causing the warning light to trigger. On older cars this can often be caused by many short journeys and the light can be eliminated with a reasonable length of motorway driving.
If this doesn’t clear the DPF, Carly says this light is usually caused by a sensor or pressure difference issue, which will cost between £135 and £205 to fix. However, if the warning light is due to the DPF needing to be replaced entirely, the price rises to between £1,753 and £2,610.
Oil warning light: £64 – £185
The oil warning light will come on when the oil temperature is too high or the oil level or pressure is too low. Carly says this is most often caused by a faulty wiring or sensor within the system, meaning the typical cost to fix the problem is between £64 and £185.
Battery warning light: £64 – £1,813
If the battery warning light comes on, it may be a sign that the battery is nearing the end of its life and needs to be replaced, or it may be due to a problem with your vehicle’s electrical system. Carly says the most common cause is the alternator.
If the problem is just a faulty plug connection it could cost as little as £64 to fix. However, if the alternator needs to be replaced the price rises to between £1,235 and £1,813.
ESC/ABS warning light: £134 – £607
On the left, the electronic stability control (ESC) warning light. Right, ABS warning lamp
According to Carly, one of the 20 most common errors that trigger this dashboard warning light is a faulty steering wheel angle sensor. Depending on the vehicle manufacturer, this may turn on the electronic stability control or the ABS warning light, or both.
Recalibrating the sensor costs as little as £134, including labour. If the sensor needs to be replaced this will increase the cost by up to £607.
Automatic transmission warning light: £134 – £662
Vehicles with automatic transmission have a warning light specifically for transmission-related problems. Brands use a variety of symbols; but these are usually the gear wheel surrounding a thermometer or an exclamation mark.
Carly says a common cause is the automatic transmission getting stuck in gear. Fixing the problem typically requires filling or changing the transmission fluid; this can cost £134, or a time-consuming valve stem replacement can cost between £473 and £662.
High voltage EV system: £64 – £1,603
Electric vehicles have their own warning lights, and the high-voltage EV system is one that is often triggered by problems with electric auxiliary heaters, which draw heat directly from the main battery pack to warm the cabin and defrost the windows in winter.
If this is due to a faulty plug connection, fixing the problem could cost as little as £64. If the problem is a control unit failure, a new one could cost between £424 and £607. But the most expensive fix is to replace the electric auxiliary heater, costing between £1,070 and £1,603, including labour.
Engine temperature warning light: If red, this symbol indicates that the engine temperature is dangerously high and overheating; The driver must stop immediately. It may be due to lack of coolant.
This is a refrigerant warning light
Coolant warning light: If the same symbol glows yellow, this indicates that the system has detected an insufficient coolant level. You should stop to prevent the engine from overheating, but be sure to let it cool completely before opening the tank and refueling.
Brake system warning light: If it is on, this may be due to some problems in the braking system, such as a decrease in brake fluid or a problem with the electronic parking brake. It may also appear alongside other brake warning lights, such as ABS or brake pad warnings.
This is a tire pressure warning light
Power steering warning light: This red warning light indicates a problem with the power steering system that must be investigated immediately.
It may be caused by insufficient power steering fluid due to leakage.
Tire pressure warning light: This light will glow amber if the vehicle’s tire pressure monitoring system detects a sudden drop in pressure or detects that one tire is significantly different from the others. It may indicate that the tire is damaged or has a flat tire.
If you have any questions contact moneymail@dailymail.co.uk.
