Car Dashboard Warning Lights: What Each Symbol Means and What to Do

What the colours mean

ISO 2575, the standard for symbols on controls, indicators and tell-tales in road vehicles, is now in its ninth edition, published in September 2021. Clause 5 sets out what each colour means, and carmakers follow it closely.

The standard also uses colour inside one symbol: on heating and cooling indicators, red means hot and blue means cold. That is why many cars show a blue thermometer after a cold start and a red one when the engine overheats.

Some warnings change colour as they become more urgent. Volkswagen's AdBlue warning starts amber and turns red once the range runs out, according to the RAC's guide to Volkswagen warning lights (October 2026). A few brands also show the engine light in red for severe faults, so always read the colour you actually see, not the one you expect.

The most common warning lights and what to do

Symbols below are described in words, as they appear on most European cars. Exact shapes and colours differ slightly by brand; your handbook has the final word. "Stop now" means pull over as soon as it is safe, switch off and do not restart until you know the cause.

Red warnings: stop as soon as it is safe

Oil pressure

TÜV Nord's advice (September 2026) is to switch off, wait a few minutes and check the dipstick. If the oil is low, top up with the grade in the handbook. If the level is correct and the light stays on, the oil pump or sensor may have failed: do not keep driving, because an engine without oil pressure can seize within minutes.

Coolant temperature

Switch off and let the engine cool. Never open the expansion tank or radiator cap while hot: the system is pressurised and the coolant can scald. If the level is fine and the light returns, call for recovery.

Charging

A red battery light while driving means the alternator is not charging. TÜV Nord warns that a broken drive belt can be the cause, and on many engines the same belt also drives the water pump, so overheating may follow. Leave the traffic flow and call for help.

Brakes

If the parking brake is fully released and the red brake light stays on, brake fluid may be low or the system faulty. Do not drive on. Pad wear is a separate amber light and is covered in our guide to brake pads and discs.

Amber warnings: drive on carefully and book a garage

An amber engine light is the most common of these, and it has its own guide: check engine light on explains fault codes, steady versus flashing and what to do. The same logic applies to the others.

ABS

Normal braking still works, but wheels can lock in an emergency stop. The RAC advises keeping extra distance and getting it checked; if the red brake light comes on at the same time, stop and call for help. ABS problems often also switch off ESC.

Airbag

The car drives normally, but airbags and belt tensioners may not fire in a crash. Have it diagnosed promptly and do not try to work on the system yourself.

ESC and TPMS

A flashing ESC light means the system is catching a slide: ease off. A steady light means it is off or faulty. A tyre pressure light needs a stop at the next fuel station to check all four tyres against the figures on the door pillar or fuel flap; many indirect systems then need resetting through the car's menu.

Diesel lights

A glow plug lamp that stays lit for a few seconds after you switch on is normal preheating. A flashing one usually means a fault. Auto Zeitung (February 2025) puts glow plug replacement at about €150-250 at a workshop in 2025, depending on the engine. The DPF lamp asks for a steady, faster drive; the full procedure and repair options are in our blocked DPF guide. For the AdBlue countdown, see AdBlue explained: once it reaches zero, the engine will not restart until you refill.

EPC

Found on Volkswagen, Audi, Skoda and Seat petrol cars, this lamp points to the throttle or engine electronics. The RAC says the car may go into a reduced-power safe mode; it is usually drivable, but have the code read straight away.

When a light flashes, stays on or never appears

A flashing light is usually more urgent than the same light lit steadily. A flashing engine light warns of misfires that can overheat the catalytic converter; a flashing ESC light means the system is working right now; a flashing glow plug light means a fault.

Every warning lamp should light briefly during the bulb check when you switch on the ignition, then go out. If the airbag, ABS or engine light never comes on at all, the bulb may have failed or been removed, which hides faults. It is a classic trick on used cars, and a reason to insist on a diagnostic scan before you buy.

Text messages on newer cars give more detail than the symbol alone. Our guide to the on-board computer explains where to find them.

Warning lights and roadworthiness tests

Several lamps decide a test result on their own. In the UK MOT inspection manual, an ABS warning lamp showing a malfunction, an ESC lamp showing a malfunction, an airbag or SRS lamp showing a malfunction, an electronic power steering lamp showing a malfunction and an electronic parking brake lamp showing a malfunction are all major defects, which means an automatic fail. The tyre pressure monitoring system is checked on passenger cars first used from 1 January 2012, and a TPMS that is malfunctioning or obviously not working is a major defect too. A lit engine light fails petrol cars first used from July 2003 and diesels first used from July 2008.

Other European tests treat lit warning lamps in a similar way. The German HU, French contrôle technique and Spanish ITV are compared in our guide to roadworthiness tests in Europe.