Dashboard warning lights can be confusing and worrying. Some mean "stop immediately," others mean "book a service soon." Here's what you need to know about every common warning light.
Understanding Warning Light Colors
Before we dive into specific lights, understand the color coding:
Red = Stop Immediately - Serious fault that could cause damage or danger - Don't drive the car - Call for assistance
Amber/Yellow = Caution - Problem needs attention soon - Safe to drive carefully to garage - Don't ignore - it will get worse
Green/Blue = Information - System is operating - Not a fault - No action needed
Critical Red Warnings (Stop Immediately)
### Oil Pressure Warning
What it looks like: Old-style oil can
What it means: Low oil pressure or level
What to do: - Stop immediately and safely - Check oil level when engine cool - Top up if low and check for leaks - If level OK but light stays on = serious problem - Don't drive - oil pressure loss destroys engines in minutes
Cost to fix: Free to £2,000+ depending on cause - Low oil: £10 top-up - Oil pressure sensor: £50-£100 - Oil pump failure: £500-£2,000+ - Engine damage: £3,000+
### Brake Warning
What it looks like: Circle with "BRAKE" or exclamation mark
What it means: - Handbrake is on (check first!) - Low brake fluid - Brake system fault - Worn brake pads (some cars)
What to do: - Check handbrake is released - If still on, check brake fluid level - Test brakes carefully at low speed - If pedal feels soft or different, don't drive - Get checked immediately if not obvious cause
Cost to fix: £50-£300 - Brake fluid top-up: Free (but find the leak!) - Brake pads: £80-£150 per axle - Brake fluid change: £50 - Master cylinder: £200-£400
### Battery/Charging Warning
What it looks like: Battery symbol
What it means: Battery not charging
What to do: - Turn off non-essential electrical items - Drive straight to garage (if close) - Engine will stop when battery drains (10-30 minutes) - Modern cars lose power steering and brakes when engine stops!
Cost to fix: £50-£400 - Loose alternator belt: £20 - New alternator belt: £50-£100 - Alternator replacement: £150-£400
### Coolant Temperature Warning
What it looks like: Thermometer in liquid
What it means: Engine overheating
What to do: - Stop as soon as safely possible - Turn engine off immediately - Don't open coolant cap while hot (risk of burns) - Let cool for 30 minutes minimum - Check coolant level when cool - Don't drive if still overheating
Cost to fix: Free to £1,500+ - Coolant top-up: Free - Thermostat: £80-£150 - Water pump: £150-£400 - Head gasket: £500-£1,500+
Important Amber Warnings
### Engine Management Light (Check Engine)
What it looks like: Engine outline
What it means: Emissions or engine fault detected
What to do: - If steady (not flashing): Book diagnostics soon - If flashing: Stop immediately - serious fault - Steady light: Usually safe to drive carefully - Can be anything from loose fuel cap to major fault
Cost to fix: Free to £2,000+ - Loose fuel cap: Free - Oxygen sensor: £100-£200 - Catalytic converter: £300-£1,500 - Major engine fault: £500-£2,000+
My tip: Get it diagnosed (£45) before guessing. I see people spend hundreds on parts they don't need!
### ABS Warning Light
What it looks like: "ABS" in circle
What it means: Anti-lock braking system fault
What to do: - Normal brakes still work - No ABS assistance (wheels can lock under heavy braking) - MOT failure if light stays on - Book diagnosis soon
Cost to fix: £50-£400 - ABS sensor: £50-£150 - ABS pump: £300-£800 (can often repair for less)
### Airbag Warning Light
What it looks like: Person with inflated airbag
What it means: Airbag system fault
What to do: - Airbags may not deploy in crash - Or could deploy randomly (rare but dangerous) - MOT failure - Book diagnosis soon
Cost to fix: £50-£800 - Loose connection: £50 - Crash sensor: £100-£200 - Airbag replacement: £300-£800
### Diesel Particulate Filter (DPF)
What it looks like: Box with dots inside
What it means: DPF needs regeneration (cleaning)
What to do: - Drive at 50mph+ for 15-20 minutes - Keep revs above 2000rpm - Light should go off after successful regeneration - If doesn't clear, book diagnostics
Cost to fix: Free to £2,000 - Successful regeneration: Free (just drive it!) - Forced regeneration: £80-£150 - DPF cleaning: £150-£300 - DPF replacement: £500-£2,000
### Tyre Pressure Monitoring System (TPMS)
What it looks like: Cross-section of tyre with exclamation mark
What it means: - Low tyre pressure detected - TPMS sensor fault
What to do: - Check all tyre pressures immediately - Inflate to correct pressure (handbook or door pillar) - If light stays on after correction, sensor fault
Cost to fix: Free to £30 per wheel - Inflate tyres: Free at most garages - TPMS sensor: £30-£60 per wheel
### Engine Temperature Warning (Blue)
What it looks like: Blue thermometer
What it means: Engine is cold (not a fault!)
What to do: - Just information - Drive gently until light goes out - Avoid high revs while cold - Normal to stay on for 5-10 minutes
Advanced Systems Warnings
### Electronic Stability Control (ESC/ESP)
What it looks like: Car with skid marks
What it means: - Flashing: System actively working (slippery conditions) - Steady: System fault
What to do: - Flashing is normal on wet/icy roads - If steady, book diagnostics - Car safe to drive but no electronic stability assistance
### Power Steering Warning
What it looks like: Steering wheel with exclamation mark
What it means: Power steering fault
What to do: - Steering will be very heavy - Still possible to steer but requires effort - Book diagnostics soon - OK for short distances
### Glow Plug Warning (Diesel)
What it looks like: Coil or spring shape
What it means: - Pre-heating engine (normal) - Or glow plug fault (if stays on)
What to do: - Wait for light to go out before starting (cold weather) - If stays on after starting, one or more glow plugs failed - Book service soon (starting will get harder)
What To Do When A Warning Light Comes On
1. Note the color - Red = stop, Amber = caution 2. Check your handbook - Exact meanings vary by model 3. Look for obvious causes - Handbrake on? Fuel cap loose? 4. Test safely - Brakes feel OK? Temperature normal? 5. Book diagnostics - Don't guess what's wrong
Common Myths Debunked
"Disconnecting the battery will clear the fault" - Clears the light temporarily - Fault still exists - Light will come back on - Can lose radio code or other settings
"It's just the sensor" - Sometimes true, often not - Sensors detect real faults - Replacing sensor without diagnostics is guessing
"I'll just ignore it until MOT" - Small faults become big expensive ones - Some lights indicate MOT failure already - Safety risk in some cases
My Diagnostic Service
For £45, I'll:
- ▸Read all fault codes
- ▸Research what they mean for your specific car
- ▸Tell you what needs fixing now vs what can wait
- ▸Give you honest advice on repair costs
- ▸Clear codes after repair to verify fix
Modern cars have computers for engine, ABS, airbags, transmission, and more - I check them all.
The Bottom Line
Don't ignore warning lights:
- ▸Some indicate immediate danger
- ▸All indicate something wrong
- ▸Small problems become expensive ones
- ▸MOT failure if lights stay on
Get it diagnosed properly rather than guessing. It's cheaper in the long run and safer.
Got a warning light on? Call me - I can usually diagnose over the phone whether it's urgent or not.