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.
If a light won't clear, our mobile car diagnostics reads every system and tells you what needs fixing now versus what can wait, and we'll handle any brake work or servicing it turns up. We come to you across the Black Country, from Halesowen to Stourbridge. For more, read our MOT preparation checklist and 5 signs your brakes need attention.