Dashboard Warning Lights Explained

Yes, it is safe to drive with the spanner light on for almost every car. An amber spanner is a service reminder rather than a fault, and the car will keep running normally with it showing. Treat it differently if the spanner is red, or if the car is also losing power or idling roughly.

That said, it is telling you something real. The service intervals exist because oil degrades, filters block and belts age, and the cars we see with the most expensive faults are usually the ones where the reminder was ignored for a year or two. Cheap now, expensive later is the whole pattern.

Stop treating it as harmless if the car is also driving differently — losing power, idling roughly, or slipping on an automatic gearbox — or if the spanner is red. On some makes it is used for transmission and engine faults, and those combinations are worth reading rather than assuming. Book it on car servicing St Helens or ring 01744 808586.

Dashboard warning lights follow a traffic-light convention: red means stop, amber means book it in, and green or blue simply means something is switched on. It holds across every manufacturer, which makes it the single most useful thing to know about your dashboard when a symbol you do not recognise appears.

It is a genuine convention rather than a rough rule, and it applies across every manufacturer, which makes it the most useful thing to know about your dashboard. A red light means continuing to drive risks damage or safety — oil pressure, coolant temperature, brakes and charging are the four that matter. An amber light means a fault is stored and the car has usually protected itself; you have days, not minutes.

Green and blue are information only: sidelights, main beam, indicators, cruise control. They are not warnings and need no action at all. The full breakdown of every symbol is in the table above, and if yours does not match anything there, send a photo of the dash and we will identify it.

Several warning lights coming on at once is usually better news than one on its own, because multiple symbols arriving together normally means a single fault rather than several. A snapped auxiliary belt takes out charging, power steering and often ABS within seconds, and a low battery throws spurious codes across several modules.

The classic is a snapped auxiliary belt: charging, power steering and often ABS all appear within seconds of each other, which looks catastrophic and is one belt. Another very common cause is a battery that has dropped below the voltage the control units expect, which throws spurious ABS, ESP, airbag and traction codes all at once. Replace the battery and they all clear.

What it does mean is that reading the codes properly matters more than usual, because chasing each symbol separately is how people end up buying three parts they did not need. See car diagnostics St Helens, or ring 01744 808586 and tell us which lights you have.

The engine management light, the airbag light, the ABS light, the brake system warning, the power steering light and, on cars fitted with it, the tyre pressure monitoring light are all MOT failures when they are illuminated.

The tester also checks the reverse: each lamp must light up when the ignition is turned on and then go out once the engine is running. So removing a bulb to hide a fault fails the test just as surely as leaving the fault there.

The practical advice is to have any of these read before the test rather than after, because a failure means a retest and usually a second trip across town. We test on our own lane, so if something does fail it is diagnosed and repaired in the same building. See MOT St Helens, the airbag light at MOT and the ABS light.

An orange spanner on the dashboard is the standard service reminder, telling you a routine service is due or close to due. Orange is the reassuring version: it follows the normal convention where amber is advisory rather than urgent, so there is no fault stored and no risk in driving on the vast majority of cars.

Orange is the reassuring version. It follows the normal dashboard convention where amber is advisory rather than urgent, so there is no need to stop, no risk in driving, and no fault stored in the engine on the vast majority of cars.

It is worth acting on rather than dismissing, though, because the reminder is tied to the manufacturer’s own interval and that interval protects your warranty and your service history. Book it in, have the service done to schedule with the right oil specification, and the light is reset properly as part of the work. If it is red rather than orange, treat it differently — that is covered on the spanner light page. Ring 01744 808586.

Resetting a warning light yourself turns the lamp off and changes nothing else. If a fault caused it, the system re-runs the same self-check and the light returns within a few miles. It also wipes the freeze-frame data recorded when the fault occurred, which makes an intermittent fault harder and dearer to find.

There is a real cost to doing it, too. Clearing the code also wipes the freeze-frame data — the snapshot of engine speed, load, temperature and fuelling captured at the moment the fault occurred. On an intermittent fault that snapshot is often the most useful evidence on the car, and once it is gone the diagnosis takes longer and costs more.

The service spanner is the one exception, because there is no fault to fix — but it should be reset as part of an actual service rather than instead of one, or your service history stops matching reality. Bring it in as it is: our diagnostic check reads stored, pending and historic codes together.

The red oil pressure light means the engine is not maintaining oil pressure, and it is the single most destructive warning light on the car. Stop as soon as it is safe and switch off. Bearings begin to fail within hundreds of yards, and it is not the same as a low oil level warning.

Oil pressure is what keeps metal surfaces apart inside a running engine. Without it, bearings begin to fail in a very short distance — this is a matter of hundreds of yards rather than miles, and the damage is not recoverable. It is emphatically not the same as a low oil level warning, which is a different symbol and far less urgent.

Do not restart it to move a bit further along. Check the level if you can, but even a correct level does not clear you to drive, because a failed pump or a blocked pick-up reads full on the dipstick. Ring 01744 808586 and we will arrange getting it here. More on the oil pressure warning light.

Cold weather alone sets the tyre pressure light off routinely, because air contracts as the temperature drops and a few degrees overnight is enough to take a correctly inflated tyre below the threshold. Check all four pressures cold against the plate in the door shut, then reset the system.

Check all four pressures against the plate in the door shut or the filler flap, set them cold rather than after a drive, and reset the system. In most cases that is the end of it.

Take it more seriously if it returns within a few days, because a slow puncture behaves exactly like cold weather at first, or if the light flashes on startup and then stays on, which usually indicates a failed sensor rather than a pressure problem. Sensors have batteries and they do expire, typically after several years. See resetting the tyre pressure light, puncture repair or ring 01744 808586.

The spanner light and the engine warning light are unrelated. The spanner is a service reminder counting down to a scheduled service, while the engine warning light means the management system has detected an actual fault and stored a code. A service clears the spanner; it will not clear an engine light.

People conflate them because both are amber and both appear without warning, but the response is completely different. A spanner means book a service when convenient. An engine light means have it read, and if it is flashing, stop.

The other practical difference is that a service will clear the spanner and will not clear an engine light, because there is a real fault behind the second one. If both are showing at once, deal with the engine light first — and mention both when you ring, because a car that is overdue a service by a long way sometimes throws an engine light for exactly that reason. See engine warning light. Ring 01744 808586.

Often you do not need a garage at first. A DPF light usually means the filter is loading with soot and is asking for a sustained run at speed so it can burn it off in a regeneration — around forty minutes at motorway speed in a lower gear will clear it on most cars.

Around forty minutes of steady driving at motorway or dual-carriageway speeds, in a lower gear than usual to keep the revs up, will clear it on most cars. The light going out on its own is the system telling you it worked.

Book it in if the light stays on after that, if it starts flashing, if a second light joins it, or if the car goes into limp mode. At that point the filter is blocked rather than loaded and driving further will not fix it. Short-journey diesels are the ones this happens to repeatedly, and if it keeps coming back the cause is usually an EGR or sensor fault rather than the filter itself. See DPF cleaning St Helens.

The airbag light means the restraint system has logged a fault and may not deploy properly in a collision, which is why it is an automatic MOT failure. The usual causes are cheap and mundane: connectors under the front seats working loose, seat belt pretensioners, clock springs, or a failing battery.

The most common causes are mundane and cheap. Connectors under the front seats work loose when seats are slid back and forth or when something is stored beneath them; seat belt pretensioners, clock springs in the steering column and crash sensors account for most of the rest. A flat or failing battery can also trigger it spuriously.

What it is not is something to leave until the MOT is due. The system is passive, so you get no warning that it has stopped working other than this light, and its entire job happens in the one second you would want it. Have it read rather than reset. See the airbag warning light or ring 01744 808586.

Warning lights do differ between makes, although the colour convention is universal and the safety-critical symbols are standardised. Beyond those, manufacturers vary and a few use the same symbol to mean different things — the spanner is a service reminder on most cars and a genuine fault indicator on a handful.

The spanner is the clearest example: a service reminder on most cars, a genuine fault indicator on a handful. The EPC light is specific to the VW group. Some makes use a car-with-a-spanner outline where others use a plain spanner, and hybrids and EVs add symbols that did not exist a decade ago.

So the table on this page covers what you will see on the vast majority of cars, and we keep brand-specific pages for the makes we see most often, including Audi, BMW and Mercedes. If your symbol is not here, photograph it and send it with your reg — identifying it costs nothing.

Ring in the morning and we can usually read a warning light the same day, and if it is a red light we will always find a way to see it. Before you travel, describe what you have got — a red oil pressure or temperature light means do not drive the car in at all.

Before you travel, describe what you have got. A red oil pressure or temperature light means do not drive it in at all, and we would rather arrange recovery than have you arrive with a worse problem than you set off with. An amber light on a car driving normally is fine to bring in.

Send the reg and a photo of the dashboard on WhatsApp and you will get a straight answer on urgency before you commit to anything. We are on Boundary Road, WA10 2PZ, Monday to Friday 8:30 till 5 and Saturday mornings. Ring 01744 808586 or see contact us.