Dashboard Warning Lights Explained - What They Mean and What to Do
Complete guide to car dashboard warning lights in the UK. Understand what red, amber, and green lights mean, which require immediate action, and when you must stop driving. Clear explanations for every common warning light.
Modern cars have dozens of warning lights, and understanding them could save you from a breakdown, expensive repairs, or even a dangerous situation. Ignoring warning lights is one of the most common causes of avoidable repair bills.
This guide explains every common dashboard warning light, what it means, how urgent it is, and exactly what action you should take.
What this guide covers:
- Understanding warning light colours
- Red warning lights (stop driving)
- Amber warning lights (attention needed)
- Green and blue lights (information only)
- What to do when a warning light comes on
- Common MOT failures related to warning lights
Understanding Warning Light Colours
Dashboard warning lights follow a universal colour-coding system:
Red Lights - Stop or Check Immediately
Red lights indicate serious, potentially dangerous issues. Many require you to stop driving as soon as safely possible.
Action: Do not ignore red lights. Pull over safely and investigate, or call for assistance.
Amber/Orange/Yellow Lights - Attention Needed
Amber lights indicate issues that need attention but are not immediately dangerous. You can usually continue your journey but should have the issue investigated soon.
Action: Safe to continue driving carefully, but book diagnosis or repair promptly.
Green and Blue Lights - Information Only
Green and blue lights are informational, indicating that a system is active or operating. They are not warnings.
Action: No action needed unless light stays on when system should be off.
Flashing vs Steady Lights
Flashing/blinking: Usually indicates more serious issue than steady light Steady: Issue present but typically less urgent
Red Warning Lights - Stop or Check Immediately
Engine Oil Pressure Warning
Symbol: Oil can or lamp shape
What it means: Engine oil pressure is critically low. The engine is not being properly lubricated.
Urgency: CRITICAL - Stop immediately
Action:
- Pull over and stop as soon as safely possible
- Turn off engine immediately
- Check oil level with dipstick (wait 2 minutes for oil to settle)
- If oil level is low, top up before restarting
- If oil level is correct, do not restart - call breakdown service
- Running engine without oil pressure destroys the engine within minutes
Common causes: Low oil level, oil leak, failed oil pump, blocked oil pickup
Engine Temperature Warning
Symbol: Thermometer in wavy lines (water)
What it means: Engine is overheating, coolant temperature is too high.
Urgency: CRITICAL - Stop immediately
Action:
- Pull over safely as soon as possible
- Turn off engine
- Do NOT open bonnet immediately (hot steam risk)
- Wait at least 15 minutes for cooling
- Check coolant level in expansion tank when cool
- Do NOT open radiator cap when hot (scalding risk)
- If coolant is low, top up with water as emergency measure
- Call breakdown if problem persists
Common causes: Coolant leak, failed water pump, stuck thermostat, failed radiator fan, head gasket failure
Warning: Continuing to drive an overheating engine causes catastrophic damage including head gasket failure and warped cylinder head. Repairs can cost thousands of pounds.
Brake System Warning
Symbol: Exclamation mark in circle or "BRAKE" text
What it means: Problem with braking system. Could be:
- Low brake fluid
- Brake system fault
- Worn brake pads (some vehicles)
- Parking brake engaged (check this first)
Urgency: HIGH - Check immediately
Action:
- First, check parking brake is fully released
- If light remains, pull over safely
- Check brake fluid reservoir level
- Test brakes gently before continuing
- If brakes feel wrong, do not drive - call breakdown
- If fluid is low, have system checked for leaks
Important: If brake pedal feels spongy, goes to floor, or brakes feel weak, do not drive the vehicle.
Battery/Charging Warning
Symbol: Battery shape with + and - symbols
What it means: Charging system is not working. Battery is not being charged.
Urgency: MODERATE TO HIGH
Action:
- Safe to continue driving, but battery will eventually drain
- Turn off non-essential electrical items (radio, heated seats, air con)
- Drive directly to garage or home
- Do not turn engine off until you reach destination (may not restart)
- Have alternator and charging system checked
Common causes: Failed alternator, broken drive belt, loose battery connections, failed battery
Note: If drive belt has failed, this may also affect power steering and water pump. Monitor for overheating.
Airbag Warning
Symbol: Person with airbag deployed or "SRS"
What it means: Fault in airbag or supplemental restraint system.
Urgency: MODERATE - Have checked promptly
Action:
- Safe to continue driving
- Airbags may not deploy in accident
- Seatbelt pretensioners may not function
- Have diagnosed by professional soon
- Usually requires dealer diagnostic equipment
Common causes: Seat belt buckle sensor fault, connector issue under seat, airbag module fault, clock spring failure (steering wheel)
MOT note: Airbag warning light illuminated is an MOT failure.
Power Steering Warning
Symbol: Steering wheel with exclamation mark
What it means: Electric power steering system fault. Steering will be heavier.
Urgency: MODERATE - Safe but harder to steer
Action:
- Steering will work but require more effort
- Safe to drive carefully to garage
- Be prepared for heavy steering at low speeds
- Have diagnosed promptly
Door/Boot/Bonnet Open Warning
Symbol: Car outline with open door indicated
What it means: Door, boot, or bonnet is not properly closed.
Urgency: CHECK IMMEDIATELY
Action:
- Stop safely
- Check all doors, boot, and bonnet are properly shut
- Check back seat passenger doors
- Ensure catches are engaged
Amber Warning Lights - Attention Needed
Engine Management Light (Check Engine Light)
Symbol: Engine outline or "CHECK ENGINE"
What it means: Fault detected in engine management system. Wide range of possible causes from minor to significant.
Urgency: MODERATE - Have diagnosed soon
Action if steady:
- Safe to continue driving normally
- Note any changes in performance
- Book diagnostic check within days
- Could be emissions-related, sensor fault, or mechanical issue
Action if flashing:
- More serious fault detected
- Reduce speed and avoid heavy acceleration
- Have diagnosed as soon as possible
- May indicate catalytic converter damage occurring
Common causes: Faulty oxygen sensor, loose fuel cap, catalytic converter issue, mass airflow sensor, spark plug or ignition coil fault, EVAP system fault
Cost to diagnose: 30-60 pounds for code reading at most garages
MOT note: Engine management light illuminated is an MOT failure (from 2018).
ABS Warning Light
Symbol: "ABS" in circle
What it means: Anti-lock Braking System fault. ABS will not function.
Urgency: MODERATE - Normal brakes still work
Action:
- Normal brakes function normally
- ABS will not activate in emergency braking
- Safe to drive but avoid situations requiring emergency stops
- Have diagnosed soon
- Usually wheel speed sensor or ABS module fault
Important: Brakes still work normally; you just do not have anti-lock protection.
MOT note: ABS warning light illuminated is an MOT failure.
Traction Control/Stability Warning
Symbol: Car with wavy lines (skidding)
If flashing: System is actively working - normal in slippery conditions
If steady: System fault detected, stability control disabled
Action:
- Safe to drive but with reduced electronic assistance
- Drive more carefully, especially in wet/icy conditions
- Have diagnosed when convenient
- Often related to ABS sensor fault
Tyre Pressure Warning (TPMS)
Symbol: Exclamation mark in tyre shape or horseshoe
What it means: One or more tyres has low pressure, or TPMS system fault.
Urgency: CHECK PROMPTLY
Action:
- Stop at next safe opportunity
- Check all tyre pressures (including spare)
- Inflate to correct pressure (sticker inside driver's door)
- If one tyre loses pressure quickly, check for puncture
- Reset TPMS if required (see vehicle manual)
Note: Driving on underinflated tyres causes:
- Poor fuel economy
- Uneven tyre wear
- Reduced handling
- Risk of tyre failure
Low Fuel Warning
Symbol: Fuel pump
What it means: Fuel level is low, typically 50-70 miles range remaining.
Urgency: REFUEL SOON
Action:
- Plan to refuel soon
- Remaining range varies by vehicle and driving
- Running completely out risks fuel pump damage
- Diesel vehicles: Running dry introduces air into fuel system, requiring bleeding
Service Required Indicator
Symbol: Spanner or "SERVICE"
What it means: Scheduled service is due based on time or mileage.
Urgency: LOW - Schedule service
Action:
- Book service within reasonable time
- Check when service is actually due
- Reset after service completed
- Does not indicate fault
Glow Plug Warning (Diesel Only)
Symbol: Coiled wire or heater element
If on briefly when starting: Normal - glow plugs heating
If flashing or stays on: Glow plug or engine management fault
Action:
- Brief illumination at startup is normal
- Wait for light to extinguish before starting in cold weather
- If flashing, have diagnosed soon
- If stays on while driving, engine management fault
Diesel Particulate Filter (DPF) Warning
Symbol: Filter with dots or smoke
What it means: DPF is becoming blocked and needs regeneration.
Urgency: MODERATE - Act promptly to avoid expensive repair
Action:
- Take car for sustained motorway/A-road driving
- Drive at 2,000+ RPM for 15-30 minutes
- This allows DPF regeneration to occur
- If light persists, have diagnosed
- Forced regeneration may be needed at garage
Prevention: Regular longer journeys prevent DPF clogging. Short trips only cause problems.
AdBlue Warning (Diesel)
Symbol: AdBlue bottle or "AdBlue Low"
What it means: AdBlue fluid level is low.
Urgency: MODERATE - Top up soon
Action:
- Top up AdBlue before it runs out
- Available at most petrol stations and motor factors
- If AdBlue runs empty, engine will not start after next switch-off
- Top up is straightforward DIY task
Green and Blue Lights - Information Only
Direction Indicators
Symbol: Green arrows left or right
Meaning: Indicator is operating. Flashing indicates turn signals active.
Note: Faster flashing than normal indicates bulb failure.
Main Beam Indicator
Symbol: Blue headlight with horizontal lines
Meaning: High beam headlights are on.
Action: Remember to dip for oncoming traffic.
Fog Light Indicators
Symbol: Headlight with wavy line through beam
Front fog lights: Green symbol, beam facing left Rear fog lights: Amber symbol, beam facing right
Action: Turn off fog lights when visibility improves. Rear fog lights must only be used in visibility under 100 metres.
Cruise Control
Symbol: Speedometer with arrow
Meaning: Cruise control is active.
Action: None required - informational.
Eco Mode
Symbol: "ECO" or leaf symbol
Meaning: Vehicle is operating in efficient economy mode.
Lane Departure / Assistance
Symbol: Car between lane markings
Meaning: Lane departure warning or lane keeping assist is active.
What to Do When a Warning Light Comes On
Immediate Response
- Stay calm - Most warning lights do not require emergency action
- Note the colour - Red needs immediate attention, amber can wait
- Check if it is flashing - Flashing usually more urgent
- Pull over safely if needed - Do not stop abruptly unless critical
For Red Lights
- Pull over as soon as safely possible
- Turn off engine (unless battery light)
- Check obvious causes (oil level, coolant, doors)
- Call breakdown service if problem is not obvious
- Do not continue driving if unsure
For Amber Lights
- Safe to continue journey in most cases
- Note when light came on and circumstances
- Book diagnosis within a few days
- Monitor for any changes in vehicle behaviour
- Check owner's manual for specific guidance
Getting Diagnosis
Options for fault diagnosis:
DIY code reader:
- OBD-II readers from 20 pounds
- Plug into diagnostic port (usually under dashboard)
- Provides fault codes
- Search codes online for meaning
- Cannot read all systems (ABS, airbags often need dealer tools)
Garage diagnosis:
- Most garages charge 30-60 pounds
- Professional equipment reads all codes
- Technician interprets meaning
- Recommendations for repair
- Cost usually refunded if repair done there
Free diagnosis:
- Some Halfords stores offer free code reading
- Some independent garages offer free checks
- Mobile mechanics often include in callout
Common MOT Failures Related to Warning Lights
Since 2018, certain warning lights cause automatic MOT failure:
Automatic MOT failures:
- Engine management light (malfunction indicator lamp)
- ABS warning light
- Airbag warning light
- Electronic stability control warning light
- Tyre pressure monitoring system light (where fitted)
- Brake system warning light
Before MOT:
- Check all warning lights are off
- Have any illuminated lights diagnosed and resolved
- Engine management light is most common failure
- Budget for diagnosis and repair before test
Learn more about MOT requirements
Summary: Quick Reference Guide
Stop Immediately (Red)
- Oil pressure - Engine damage imminent
- Engine temperature - Overheating damage
- Brake system - Potential brake failure (after checking parking brake)
Check Urgently (Red)
- Battery - Will strand you
- Airbag - Safety compromised
- Power steering - Harder to steer
Attention Needed (Amber)
- Engine management - Wide range of causes
- ABS - Normal brakes work
- Traction control - Reduced stability assistance
- DPF - Needs regeneration drive
- Tyre pressure - Check and inflate
Low Priority (Amber)
- Service due - Schedule when convenient
- Low fuel - Refuel soon
- AdBlue - Top up within 500 miles
Information Only (Green/Blue)
- Indicators, fog lights, cruise control, eco mode - System status indicators
Golden rule: When in doubt, pull over safely and call for professional advice. The cost of a callout is far less than engine or transmission damage from ignored warning lights.
Related Repair Guides
- DIY Car Repair Guide - What You Can Fix Yourself
- Common MOT Failures and How to Fix Them
- How to Replace a Car Battery