Common Car Warning Lights: What Each Symbol Means and Whether You Can Drive

What the colour of a warning light actually tells you

Warning lamps are colour coded to urgency, using the same three colours you obey at a junction.

• Red — stop as soon as you can do so safely. The system is either unsafe or about to damage itself.
• Amber or orange — a fault has been stored. The car is usually drivable, but the protection or the performance you normally have is reduced.
• Green, blue or white — information. A feature is switched on and working.

Almost every lamp illuminates for a second or two when you switch the ignition on. That is the modules running their self-checks and proving the lamp works, and it is normal. What matters is which lamps are still lit once the engine has caught and you have pulled away.

A lamp that never illuminates at all is its own fault. If the airbag or ABS lamp does not appear during the self-check, either the lamp has failed or the module behind it is no longer speaking to the cluster — and an MOT tester treats that exactly as they would treat one stuck on.

Flashing is not universally worse, which is where a lot of advice goes wrong. A flashing engine management lamp is far more serious than a steady one, because it signals an active misfire dumping unburnt fuel into the catalytic converter. A flashing stability control lamp is the opposite: it means the system is working and intervening on a slippery surface. Learn what flashing means on the specific lamp rather than applying one rule to all of them.

The limit of the colour code is worth stating plainly, because the rest of this page turns on it: colour tells you urgency. It does not tell you depth. A red lamp is not necessarily an expensive repair, and an amber one is not necessarily a cheap one.

Common car warning lights and what each symbol means

Symbol shapes vary between manufacturers, so treat this as the common set and check your handbook for anything unfamiliar. The safe-to-drive answers are deliberately conservative: where a fault could reasonably be trivial or serious, the advice assumes serious.

Colour	Symbol	What it means	Is it safe to drive?
Red	Brake system — exclamation mark in a circle, brackets either side	Handbrake still applied, brake fluid below minimum, or a fault in the hydraulic circuit.	No, unless it goes out the instant the handbrake is fully released. If it stays lit, stop safely and arrange recovery.
Red	Brake system and ABS lit together	Both the hydraulic circuit and the anti-lock system are reporting. Brake force distribution may no longer be controlled.	No. Slow gradually, stop as soon as it is safe, and do not drive it to a garage.
Red	Oil pressure — an oil can with a drip	Oil pressure has fallen. That is not the same as the level being low.	No. Switch off immediately. An engine without oil pressure damages its bearings in seconds, not miles.
Red	Engine temperature — a thermometer in waves	The engine is overheating: coolant low, not circulating, or a failed fan, thermostat or water pump.	No. Stop, switch off and let it cool. Never open a hot expansion tank.
Red	Battery charging — a battery with plus and minus terminals	The charging system is not replenishing the battery. Alternator, drive belt or wiring.	Only far enough to reach somewhere safe. The car is running on stored charge and will stop when it runs out.
Red	Airbag or SRS — a seated figure facing a circle	A fault in the restraint system. An airbag or a seatbelt pretensioner may not fire in a collision, or could fire when it should not.	Mechanically yes — but the protection you are relying on is not there. Have it seen straight away. It is also an MOT failure.
Red	Power steering — a steering wheel with an exclamation mark	Steering assistance has been cut. On an electric system this is the motor or its control unit rather than fluid.	No. Assistance can disappear without warning, and the steering goes heavy exactly when you need it most.
Red	Seat belt — a seated figure with a belt across it	Someone is unbelted, or a bag on a seat is triggering the occupancy sensor.	Not a fault. Belt up, or move the object.
Red	Door, bonnet or boot open	A closure is not latched.	No. Stop and shut it properly.
Amber	Engine management (MIL) — an engine block outline	The engine or emissions system has stored a fault: anything from a loose fuel cap to a failed sensor or a misfire.	Steady: drive gently and have the codes read within days. Flashing: stop. An active misfire destroys the catalytic converter quickly.
Amber	ABS — the letters ABS inside a circle	The anti-lock function has been disabled by the ABS module. Ordinary braking is unaffected.	Yes, with care. Leave more room and brake earlier — the wheels can lock in an emergency stop. It is an MOT failure.
Amber	ESP, ESC or traction control — a car with skid marks behind it	Flashing means the system is intervening. Steady means it is switched off or faulty.	Flashing on a wet or icy road is normal. Steady on a dry road in normal driving means it is not protecting you.
Amber	DPF — a filter box with dots inside (diesel)	The particulate filter is loaded with soot and has not completed a regeneration.	Short term yes, and a sustained run at motorway speed often clears it. If it stays lit or power drops away, have it looked at.
Amber	Glow plug — a coiled filament (diesel)	Normal for a few seconds before a cold start. Lit or flashing while driving is an engine management fault.	Yes, but have the codes read. Flashing usually accompanies a stored fault rather than a cold morning.
Amber	Tyre pressure (TPMS) — a horseshoe cross-section with an exclamation mark	One or more tyres are below pressure, or a sensor or valve has failed.	Only as far as somewhere you can check all four pressures. Reduce speed and avoid hard braking.
Amber	Brake pad wear	The wear sensor has reached the pads’ limit.	Yes, but book it in now. The lamp comes on with a margin left, and that margin is finite.
Amber	Coolant level	The expansion tank has dropped below its minimum mark.	Yes, briefly. Top up once the engine is cool, and find out where it went if it keeps dropping.
Amber	AdBlue or exhaust fluid low (diesel)	The AdBlue tank is running down. Ignoring it eventually prevents the engine restarting.	Yes. Top it up before the countdown on the display runs out.
Amber	Water in fuel (diesel)	Water has collected in the fuel filter and needs draining.	Only briefly. Water reaching the injection system does serious damage.
Amber	Bulb failure	An exterior lamp, or the module driving it, has failed.	Yes, but a lamp that is out is an MOT failure and a hazard after dark.
Amber	Headlight or adaptive lighting fault	A headlight control module, levelling motor or xenon ballast has reported a fault. The beam may be fixed, dimmed or out on one side.	Yes in daylight. After dark, treat it as a lighting defect and get it corrected.
Amber	Gearbox fault, or a flashing gear position display	The transmission control unit has stored a fault and may have dropped the car into limp mode.	Limited. Limp mode can hold a single gear, so keep the journey short and avoid fast traffic.
Amber	Immobiliser or key — a car outline with a key or padlock	The immobiliser has not recognised the key, or the system has stored a fault.	If it has started, yes. If it flashes and the engine will not crank, it will not start at all.
Amber	Service due — a spanner	A time or mileage interval has been reached.	Yes. This is a reminder, not a fault.
Amber	Low fuel	The tank has reached its reserve.	Yes, briefly. Running an in-tank pump dry draws sediment through it and shortens its life.
Green	Side lights, dipped beam, indicators, front fog lights, cruise control set, stop-start active, parking sensors	The feature named is switched on and working.	Yes. These confirm a system is active rather than warn of a fault. Rear fog lights are the one to watch — left on, they dazzle the car behind.
Blue	Main beam	Full beam headlights are on.	Yes. Dip for oncoming traffic and for anyone you are following.

Why the same symbol can mean two different repairs

Nothing on your dashboard is wired directly to the part that failed. A sensor measures something, a control module decides whether that measurement is acceptable, and the instrument cluster lights the lamp the module asks for. Three links in a chain — and the fault can sit at any one of them.

What is being measured. The common case, and usually the cheap one. A wheel speed sensor packed with brake dust, a connector under a seat disturbed when someone slid it forward, a fluid level that has genuinely dropped, a pressure sensor that has drifted. Clean or replace the item and the lamp goes out.

What is doing the measuring. Every one of these systems has a control unit of its own: the ABS module bolted to the hydraulic pump, the steering ECU on the column or the rack, the airbag module under the centre console, the body control module behind the dash. When the board inside one of those fails, it reports a fault that is not out there, or it stops reporting at all. Solder joints crack under heat cycling and vibration, internal power supply stages fail, and a water leak into a footwell finds a connector long before anyone notices the damp carpet.

What is doing the displaying. The instrument cluster is a computer with a screen. When its display drivers fail it can light a lamp with nothing behind it, fail to light one that should be lit, or lose segments, backlighting, needles and the odometer along with it.

You cannot separate these three by looking at the dashboard, but their behaviour over time gives them away:

• A code that returns the moment it is cleared, with no driving in between, is being reported live rather than remembered.
• A fault that survives replacement of the part the code named — especially the second identical part — has almost certainly been misattributed.
• Several unrelated lamps arriving together, or a display that flickers or dims alongside them, points at the cluster or at low system voltage rather than at four systems failing on the same morning.
• A module that will not answer at all on a diagnostic scan is not reporting a fault. It is the fault.

None of that means every warning light is a module failure. Most are not, and starting with the sensor, the fluid or the connector is the right order to work in. The point is knowing what to conclude when that does not work, and asking the question the dashboard cannot answer for you: is the part it names broken, or is the thing doing the naming broken?

The warning lights that point at an electronic module

Several of the lamps in that table sit in front of units we repair at circuit level in an ESD-safe workshop, rather than replace. One of them deliberately belongs elsewhere. Here is where each one leads.

ABS and ESP lamps

Anti-lock braking and stability control share hardware. On most cars they share the same hydraulic modulator and the same control unit, which is why the two lamps so often arrive together and why a fault in one takes the other with it. Add the traction control lamp and, on some cars, the speedometer or the cruise control dropping out, and you are usually looking at one unit rather than three problems.

The failures inside these modules are the ones you would expect of something bolted to the engine bay and heat cycled every journey: cracked solder on the valve and pump driver circuits, failed solenoid drivers, corrupted internal memory. The tells are a code that returns instantly after clearing, a module that does not respond on the diagnostic bus, or an ABS lamp lit with no wheel speed sensor fault stored anywhere.

If you want the background first, we explain what an ABS pump is and how it works and what ESP is on a car. If a repair has already been carried out and the lamp is still on, resetting the ABS light covers what does and does not clear it. The service itself sits under ABS pump and module repairs.

One line from the table bears repeating: an ABS lamp on its own leaves you with ordinary brakes. An ABS lamp with the red brake lamp does not.

Airbag and SRS lamps

Restraint systems are handled differently here, and deliberately. An airbag control module stores crash data and fires pyrotechnic devices, so it is not a send-it-in-and-see job — careless handling can deploy a bag on a bench. If your airbag or SRS lamp is lit, contact us and we will tell you which module your car uses, what has to happen before it comes out, and whether the fault is repairable at all. In the meantime, do not start probing the connectors under the seats with the battery connected.

Power steering and EPS lamps

On an electric system there is no fluid to check. The assistance comes from a motor and an ECU mounted either on the steering column or on the rack, and the lamp appears when that ECU can no longer trust its torque sensor readings, cannot drive the motor, or has failed internally. Steering that is heavy from cold and normal once warm, assistance that comes and goes, or a wheel that stiffens on one lock only are all consistent with the unit rather than the mechanical rack. Our write-up of Peugeot 207 power steering failure works through one of the best documented examples, and EPS and steering repairs is where those units are rebuilt.

When the dashboard itself is the fault

Sometimes the messenger is what has broken. Dead pixels or a blank LCD, backlighting that fails in patches, needles that stick or sweep to full, a mileage readout that flickers or flashes, warning lamps lit with no system reporting a fault behind them — those are cluster symptoms, not system symptoms. Instrument cluster repairs covers that work.

Headlight and adaptive lighting faults

A lighting fault lamp is not always a bulb. Xenon and LED systems run through a ballast or an igniter, and adaptive systems add levelling motors and a control module that steers the beam with the wheels. When the module fails, the beam can stay fixed, drop to a permanent dipped position or go out entirely while the bulb is still perfectly good. Headlight control module repairs deals with those units.

Engine management and turbo faults

The engine management lamp is the one on this list we do not take in. Repairing a failed engine ECU is the specialism of ecu-repairs.com, an independent specialist, and turbocharger faults — which frequently light the same lamp alongside a loss of boost and a smoke complaint — belong with our turbo specialists at turbo-repairs.com, our sister site for everything turbo. Getting the fault codes to the right specialist first is faster than posting a unit to the wrong one.

The DPF lamp

A DPF lamp is about soot rather than electronics. The road legal answer is regeneration or professional cleaning: a filter that will still accept a regeneration usually clears with a sustained run at motorway speed once the exhaust is properly hot, and one that will not needs cleaning off the car. What a DPF is and how it works explains the cycle and why short journeys defeat it. DPF removal is a motorsport and off-road service only — a vehicle without a working filter cannot lawfully be used on a UK road. If the lamp keeps returning after a clean, suspect the differential pressure or exhaust temperature sensors rather than the filter itself.

If you already know which unit is at fault, or you have a fault code and want it looked at, send the details through our repair form. Include the codes, the make, model and year, and what the car actually does — that description is what the bench work is aimed at, because units are run on our own hardware-in-the-loop rigs until they repeat the behaviour you reported. What we repair lists the full range of units.

Which warning lights fail an MOT

An illuminated warning lamp is not only advice. Several are MOT failures in their own right, which changes how long you can reasonably leave one.

Under the DVSA MOT inspection manual, a lamp indicating a malfunction is a defect for the engine management system, the anti-lock braking system, the airbag and restraint system, electronic power steering, and the brake fluid level warning. On cars first used from 1 January 2012 onwards, the tyre pressure monitoring lamp is checked too, along with electronic stability control where it is fitted.

A lamp that does not work at all is treated the same way. The tester watches the ignition self-check to confirm each of those lamps illuminates and then goes out, so a removed bulb, a taped-over lamp or a cluster whose display has failed is a failure rather than a way round one.

The practical consequence is worth planning for: an amber lamp that feels tolerable in August is not tolerable in the week the MOT is due, and a unit that has to be posted, repaired and refitted is not a same-day job.

What to do when a warning light comes on

1. Read the colour first. Red means find somewhere safe and stop. Amber means you have time to think, but not indefinitely.
2. Note what the car was doing. Speed, engine temperature, how long since it started, the weather, whether it had just been jump started or had the battery disconnected, and whether anything felt different. Intermittent faults are diagnosed from exactly this kind of detail, and it is gone if nobody writes it down.
3. Do the checks that cost nothing. Handbrake fully off. Fluid levels once the engine is cool. All four tyre pressures. Fuel cap clicked shut. Doors, bonnet and boot properly latched. A surprising share of warning lamps end here.
4. Get the codes read, and recorded before anything is cleared. Clearing a code takes the freeze frame data, the timestamp and the occurrence count with it. On an intermittent fault that record is the single most valuable thing you have, and it cannot be recovered.
5. Ask which module reported it. A scan tool names the module that stored the code, not only the code. That is the first real narrowing between a failed sensor, a failed control unit and a failed cluster.
6. Be wary of the second identical part. If replacing the component the code named changed nothing, fitting another one rarely will. Move to the wiring on that circuit, then to the module at the end of it.

Clearing codes is the last step of a repair, not the first step of a diagnosis. Anyone who clears them before they are written down has made the next fault harder to find.

Warning lights on your make of car

Symbol sets are not fully standardised. The core safety lamps follow international convention and look broadly the same across manufacturers, but generic amber fault lamps, driver information messages and the wording on the trip display are manufacturer specific, and the same shape does not always carry the same meaning.

We have detailed guides for several of the sets that come up most often:

• Vauxhall warning lights and symbols
• Vauxhall Corsa warning lights, by generation
• Vauxhall Astra warning lights and the message centre
• Peugeot dashboard warning lights and symbols
• Peugeot 3008 warning lights and the i-Cockpit screen
• VW Polo warning lights, by generation
• VW Caddy warning lights on a working van
• Fiat 500 warning lights and the amber triangle
• Ford Focus warning lights, Mk1 to Mk4
• Ford Puma dashboard symbols
• Ford Ka warning lights and symbols
• Ford Kuga warning lights, petrol to plug-in hybrid
• Fiat 500 flashing mileage display
• A flashing PRNDS gear position display

If your make is not covered yet, work from the table above, then confirm the symbol against the handbook — and treat any lamp the handbook does not list as amber until you know otherwise.

Common car warning lights FAQs