Dashboard warning light on? What it means and what to do

Warning lights follow a simple colour code. Red means stop as soon as it's safe — low oil pressure, overheating and the red brake warning can all mean serious damage or reduced braking. Amber means something needs attention soon, but you can usually keep driving gently.

Find your light below for the likely causes, ranked, and what to do next.

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Warning light on

Is it petrol or diesel?

A hybrid counts as petrol. The likely causes are completely different between the two.

Is it safe to keep driving?

For a typical car with each symptom. These are general guidance, not a diagnosis — if you're unsure, don't drive it.

Red oil warning light

Stop — don't drive it

If you're driving, pull over when it's safe and switch off. Don't drive it again until it's been checked — have it recovered if you need to. Carrying on risks the engine, your brakes or your steering, and recovery costs less than the damage.

Likely causes

  1. Low oil level or oil pressureMost likely

    Stop and switch off. Check the dipstick with the car on level ground after a few minutes. Driving with the oil light on can destroy an engine in minutes.

    If it's this: don't drive.

  2. Engine or gearbox oil leakLikely

    Dark brown drips under the engine, an oily underside, and a burning smell if it's dripping onto the exhaust.

    If it's this: get it checked soon.

  3. Wet timing belt breaking up in the oilPossible

    The oil light comes on even though the dipstick reads full, or the brake pedal goes hard. Only some engines run their timing belt in oil — if this one does, stop and get it checked before driving further.

    If it's this: don't drive.

What to do next

Stop and switch off now. Check the level on the dipstick after a few minutes. If it's full and the light stays on, don't restart it — have it recovered.

Red battery (charging) light

Get to a garage today

The car will keep running only until the battery goes flat. Head for a garage now rather than booking it in for later, and don't switch off anywhere you'd be stuck if it didn't restart.

Likely causes

  1. Alternator not chargingMost likely

    The red battery light is on while driving. With the engine running, a meter across the battery should read about 13.8–14.7V; much lower means it isn't charging.

    If it's this: get it checked soon.

  2. Auxiliary (fan) belt slipping or wornLikely

    A squeal on start-up or at full steering lock, and a glazed or cracked belt. If it snaps, you lose charging and often the water pump.

    If it's this: get it checked soon.

  3. Flat or failing 12V batteryPossible

    The dash and interior lights are dim or die when you try to start. If a jump start fires it straight up, you've found it.

    If it's this: not urgent.

What to do next

The car is running on battery alone and will stop when it's flat. Turn off everything you don't need and get to a garage — don't switch off somewhere you can't get help.

Red temperature or coolant light

Stop — don't drive it

If you're driving, pull over when it's safe and switch off. Don't drive it again until it's been checked — have it recovered if you need to. Carrying on risks the engine, your brakes or your steering, and recovery costs less than the damage.

Likely causes

  1. Coolant leak (hose, radiator or water pump)Most likely

    The coolant is below MIN when the engine is cold, there's a sweet smell, and a puddle under the front of the car.

    If it's this: get it checked soon.

  2. Thermostat or radiator fanLikely

    The gauge climbs in traffic and drops on the move (fan), or the heater never gets properly hot (thermostat stuck open).

    If it's this: get it checked soon.

  3. Head gasketPossible

    Thick white sweet-smelling smoke, coolant disappearing with no visible leak, and bubbles in the expansion tank with the engine running.

    If it's this: don't drive.

  4. Auxiliary (fan) belt slipping or wornPossible

    A squeal on start-up or at full steering lock, and a glazed or cracked belt. If it snaps, you lose charging and often the water pump.

    If it's this: get it checked soon.

What to do next

Pull over and switch off. Don't open the coolant cap while it's hot. Driving an overheating engine turns a cheap hose into a new cylinder head.

Red brake warning light

Don't drive it until you've checked

A red brake light can mean the brake fluid is low or there's a fault in the braking system — or just that the handbrake isn't fully off. Check the handbrake first. If the light stays on with it released, don't drive the car: have it checked or recovered.

Likely causes

  1. Leaking brake hose or corroded brake pipeMost likely

    A spongy pedal, the brake fluid level dropping, and a wet patch on the inside of a wheel.

    If it's this: don't drive.

  2. Worn brake padsLikely

    A squeal when braking, a pad-wear warning light, or less than 3mm of pad material left. Grinding means they're down to the metal.

    If it's this: get it checked soon.

  3. Handbrake cable or electronic parking brakeLikely

    The lever pulls up further than it used to, the car rolls on a slope, or an EPB fault light is on.

    If it's this: get it checked soon.

What to do next

Check the handbrake is fully off and the brake fluid is between MIN and MAX. If the fluid is low or the pedal feels different, don't drive it.

ABS or traction control light

Drive carefully — book it in

You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.

Likely causes

  1. ABS wheel-speed sensorMost likely

    The ABS and traction-control lights come on together. The fault code names the wheel. Normal braking still works; the anti-lock doesn't.

    If it's this: get it checked soon.

  2. Flat or failing 12V batteryPossible

    The dash and interior lights are dim or die when you try to start. If a jump start fires it straight up, you've found it.

    If it's this: not urgent.

  3. Worn brake padsPossible

    A squeal when braking, a pad-wear warning light, or less than 3mm of pad material left. Grinding means they're down to the metal.

    If it's this: get it checked soon.

What to do next

Normal braking still works, but the anti-lock doesn't — leave more room in the wet. The fault code will name the wheel sensor.

DPF light (diesel)

Drive carefully — book it in

You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.

Likely causes

  1. Blocked diesel particulate filter (DPF)Most likely

    The DPF light is on, sometimes with limp mode. If the car mostly does short trips, a steady 20-minute run at motorway speed can clear it — if the light stays, it needs a forced regeneration.

    If it's this: get it checked soon.

  2. EGR valve stickingPossible

    A rough idle, black smoke and a P0400-series code. Common on diesels that do mostly short, slow journeys.

    If it's this: get it checked soon.

  3. AdBlue system or NOx sensorPossible

    An AdBlue warning or a countdown to no-start on the dash. Top up the AdBlue first; if the warning stays, it's usually a sensor or the heater.

    If it's this: get it checked soon.

What to do next

Try a steady 20-minute drive at 50–70mph to let it regenerate. If the light stays on or goes into limp mode, book it in soon — a clogged DPF left long enough becomes a very expensive one.

Glow plug light flashing (diesel)

Drive carefully — book it in

You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.

Likely causes

  1. Glow plugs or glow plug relayMost likely

    Hard to start when cold, fine once warm, and it gets worse week by week. A garage can test each plug in about ten minutes.

    If it's this: get it checked soon.

  2. EGR valve stickingLikely

    A rough idle, black smoke and a P0400-series code. Common on diesels that do mostly short, slow journeys.

    If it's this: get it checked soon.

  3. Blocked diesel particulate filter (DPF)Possible

    The DPF light is on, sometimes with limp mode. If the car mostly does short trips, a steady 20-minute run at motorway speed can clear it — if the light stays, it needs a forced regeneration.

    If it's this: get it checked soon.

  4. Turbocharger or a leaking boost pipePossible

    A whistle or hiss under acceleration, loss of power, and sometimes blue or black smoke.

    If it's this: get it checked soon.

What to do next

On many diesels a flashing coil light is the engine's general fault warning, not just the glow plugs. Have the code read.

Tyre pressure warning light

Drive carefully — book it in

You can drive gently, but get it looked at within days rather than weeks. Left alone it will get worse, less safe or more expensive.

Likely causes

  1. Damaged or under-inflated tyreMost likely

    Check the pressures, and look for a bulge on the sidewall or a nail in the tread. A bulge means the tyre can fail — replace it before driving at speed.

    If it's this: get it checked soon.

What to do next

Check all four pressures with a gauge (including the one that looks fine) and look for a nail. If one keeps dropping, it's a slow puncture.

A shortlist, not a diagnosis

The ranking is the one a mechanic would give over the counter for a typical car — nobody can road-test a car over the internet, and the real cause may not be listed. Add the registration in the checker above to have it checked against that car's MOT advisories, mileage and engine. Have the car checked by a qualified mechanic before relying on it, and if you're unsure whether it's safe, don't drive it.

Common questions

Which warning lights mean stop driving?

Red ones, as a rule. The oil pressure light, the temperature light and the red brake warning all mean pull over when it's safe and switch off. The red battery light is less immediate — the car keeps running on its battery until it goes flat — but get to a garage the same day. Amber lights such as ABS, DPF or tyre pressure mean book it in soon.

Can I drive with the ABS light on?

Your normal brakes still work, but the anti-lock system — and often traction and stability control — may not, so the wheels can lock under hard braking on a wet road. Drive gently, leave more room, and get it checked within days. If the red brake warning comes on as well, stop.

What should I do when the DPF light comes on?

It usually means the filter needs to clean itself, which takes a steady, faster drive — check the handbook, but most ask for around 20 minutes at a steady speed on a dual carriageway or motorway. If the light stays on, starts flashing or the car goes into limp mode, get it looked at before the filter blocks completely.

Why is the glow plug light flashing while I drive?

On many diesels a glow plug light that flashes while you're driving is the engine's general fault warning. It can be the glow plugs themselves, but EGR, DPF and boost-pressure faults trigger it too, and the fault code tells you which.

Related symptoms

Engine management light

Engine management light on: causes and is it safe to drive?

Brakes

Brake problems: squeaking, grinding, judder or a soft pedal

Won't start

Car won't start? Find the likely cause

All symptoms: Engine management light · Won't start · Exhaust smoke · Running poorly · Leaks · Brakes · Steering & vibration · Noises · Symptom checker