What to do if a warning light is on

Car warning lights are supposedly the stuff of nightmares but in truth, the majority aren’t worth losing one wink over, let alone 40

James Wilson
Sep 20, 2021

A warning light appearing on your dashboard can be the cause for real panic - and nobody would blame you for doing so. A potentially huge incoming repair bill, being stranded on the side of the road or even the death of your car are just some of the outcomes that are likely to spin around in your mind at that moment.

The reality, however, is that car warning lights often signify much less dramatic issues. Many new cars have an array of sensors and systems that will alert you if anything is even slightly out of the ordinary. That said, it could still be a serious fault, even if the odds are somewhat against this, so understanding what a warning light means and what to do when it shows are important.

It's easy to assume that the appearance of a warning light is a signal of doom that the car will soon need to be scrapped. The engine management light (EML) in particular is one that can strike fear into the heart of a motorist. Quite often though, an EML is due to a fault with one of the sensors monitoring the engine rather than the engine itself. If that's the case, the fix can be cheap and simple. However, the key thing is to get any lights checked early, you don't want to ignore this warning, as something small could become more serious if not attended to.

Read on to wash away the hysteria surrounding car warning lights and to get a clear feel for what to do should one appear on your dashboard. There will be no need to memorise the meaning of every single warning light, either, as the majority can be found in our dedicated warning light article. Remember that the car's manual should have an explanation for what any unusual symbols - or lights that are unique to your car - mean.

What to do when a car warning light comes on

Find a safe place to stop and pull over

Unless the meaning of a warning light is obvious and there is no need for immediate concern - such as the fuel light when you're aware you need to fill up - the first thing to do is to find a safe place to stop and investigate. This should be simple on paper, but in reality factors such as traffic, the speed you're travelling, road type (especially if you're on a busy motorway with no hard shoulder) and the severity of the car’s problem all come into play and must be evaluated relatively quickly.

Be calm and assess the situation - stopping in a dangerous place or slamming on the brakes on a busy road poses much more danger than the likely problem. When driving on the motorway or a dual carriageway, calmly move to the inside lane and come off at the next junction - provided there are no unusual sounds, smells or noises. If getting to the next turnoff is not possible - for example, if the car has lost all power - then pull onto the hard shoulder.

If there is no hard shoulder, pulling as far to the left of the inside lane as possible is the next best option. In such scenarios (where a faulty car is blocking part or all of a lane on a high-speed road) it is best to get out of the car and stand well back from the road and call a recovery service. It may be dark, cold and raining, but remember you are typically much safer being out of the car than being in a marooned car on a fast road.

If your car is still moving but has suffered a loss of power, it's possible it has gone into ‘limp home mode’ which reduces the amount of power the engine can produce should certain warning lights come on (such as an EML) to help protect it from damage. What this means is that there is no need to panic if a warning light comes on and a car becomes sluggish, it has been designed to do this. Just make sure you're in a suitable lane - if the car has limited you to 30mph on a motorway, you'll want to move to the inside lane as soon as you can, and make sure to get off the motorway at the first opportunity.

If driving on a regular single carriageway, normal rules for stopping should be adhered to unless it is an emergency, e.g. don’t stop on double yellow lines. It is worth remembering if a warning light comes on and it is accompanied by loud noises, strange smells and any indication of steam/smoke from under the bonnet that the problem is likely to be serious - or could become serious if you ignore it - so you should stop as soon as possible.

Assess the situation

Once stopped in a safe location assessing the situation is the next step. Take a look at the owner's manual; these are usually stored in the glovebox or in a tray under one of the front seats. If you don’t have a hard copy for whatever reason, you can usually find what you're looking for online, some manufacturers even have smartphone applications that function much like an owner’s manual.

Typically an owner’s manual will have a summary section detailing all the warning lights which might come up and an accompanying list of suggested actions to take. Often the index at the back of an owner’s manual is the best way to locate such a page. Headings along the lines of ‘dashboard warning lights’ or simply ‘warning lights’ are commonplace, but failing that, look for a specific warning light (such as engine management light) as it could well be listed on a page along with all the other warning lights.

If you have no access to an owner's manual and the internet has failed you then all is not lost - often the meaning and severity of a warning light can be sussed out by using our car dashboard light article, as many symbols are relatively standard across different cars.

Take action

Following the instructions in the car’s owner’s manual is the best first move following a warning light appearing. That said, it is important to use a bit of common sense when deciding on what to do.

If, for example, a light has come on and it means the traction control - a system that stops the wheels from spinning when accelerating - is faulty, a manufacturer may well recommend going straight to a garage.

The truth is, though, a car does not need traction control to function so it could be driven indefinitely without ever fixing the issue. At the same time, drivers who regularly find themselves on muddy, snowy or rainy roads - or those who often drive hard and regularly activate the traction control - will definitely appreciate functioning traction control, so a quick trip to the garage should be high on their to-do list.

Fix the issue

It is often easy to make a mountain out of a molehill when it comes to car warning lights and that extends to fixing them. Simply turning a car off and on again can sometimes get rid of unwanted dashboard lights that are the result of electrical gremlins.

If that doesn’t work (or a warning light repeatedly comes on and off), a trip to the garage may well be required. Handily, all modern cars come with on-board diagnostics - in simple terms, this means there is a socket for mechanics to plug a special computer into to see what is causing a warning light to appear.

After diagnosing the issue, a garage will be able to reset/wipe the software, which saves faults or identifies which components need to be replaced. If new parts are installed, a car’s on-board computer should automatically realise the issue has been fixed, but if a warning light stays on, the software can be manually reset/wiped for good measure.


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