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🚨 Complete Reference Guide

Car Dashboard Warning
Lights Explained

📅 Updated March 2025
💡 40+ warning lights covered
🇬🇧 UK cars

Warning light just come on? This guide covers every common dashboard warning light — what the symbol means, how serious it is, whether it's safe to keep driving and exactly what to do next. Bookmark this page for future reference.

Red — Stop / Act immediately
Amber — Caution / Get checked soon
Green — Information only
Blue — Information only
Red Warning Lights — Stop or Act Immediately
🛢️
Oil Pressure Warning
Stop Immediately
Oil is not circulating at sufficient pressure. Engine components are being damaged right now without lubrication. This is the most critical warning light on your dashboard.
→ Pull over safely, switch off engine immediately. Do not restart. Call for recovery.
🌡️
Engine Temperature (Red)
Stop Immediately
Engine is overheating. Could be low coolant, a failed thermostat, water pump failure or a blown head gasket. Continued driving causes severe engine damage within minutes.
→ Stop safely, switch off engine. Let cool for 30+ minutes before checking coolant. Never remove cap when hot.
🔋
Battery / Charging Warning
Urgent
Battery is not being charged — alternator may have failed or a drive belt broken. Your car is running on battery power only and will cut out within 20–60 minutes.
→ Drive directly to a garage or home. Turn off all electrics (AC, heated seats, stereo) to extend range. Don't switch off engine.
🅿️
Brake System Warning
Stop Immediately
Could indicate low brake fluid, a brake fluid leak or a fault in the braking system. If brakes feel normal it may just be the handbrake left on — check first. If brakes feel spongy, stop immediately.
→ Check handbrake is off. If brakes feel abnormal, stop the car safely right away.
🛡️
Airbag / SRS Warning
Do Not Drive
A fault in the airbag or seatbelt pretensioner system. Airbags may not deploy in a collision — or could deploy unexpectedly. This is a safety-critical fault.
→ Get the fault diagnosed before driving. This needs specialist equipment to diagnose properly.
🔐
Power Steering Warning
Urgent
Electric or hydraulic power steering has failed. The car can still be steered but requires significantly more effort — dangerous at low speeds and in tight manoeuvres.
→ Drive with care directly to a garage. Avoid motorway driving without power steering.
🚗
Door / Boot Ajar Warning
Check Now
A door, boot or bonnet is not fully closed. Check all doors including the boot. If all appear closed the sensor or latch may be faulty.
→ Stop and check all doors are firmly shut before continuing to drive.
⛽
Low Fuel Warning
Refuel Soon
Fuel level is critically low — typically around 10–15 miles of range remaining depending on the car. Running completely dry can damage the fuel pump on some vehicles.
→ Refuel as soon as possible. Don't rely on reserve range estimates.
Amber Warning Lights — Get Checked Soon
⚙️
Engine Management Light
Get Checked This Week
A fault has been detected in the engine, exhaust or fuel system. Over 1,000 possible fault codes. Can be as minor as a loose fuel cap or as serious as a failing catalytic converter. Flashing EML = stop driving immediately.
→ Check fuel cap first. Get a diagnostic. EML on = automatic MOT fail. Full EML guide →
🛢️
Low Oil Level
Top Up Today
Oil level has dropped below the minimum. Different from the red oil pressure light — there's still oil present but not enough for sustained driving. Do not confuse with the red oil pressure warning.
→ Check dipstick, top up with correct grade oil. Investigate reason for oil loss. Full guide →
🔄
ABS Warning Light
Get Checked Soon
Anti-lock braking system has a fault. Normal braking still works but ABS won't prevent wheel lock in emergency braking. Also causes MOT failure. Common cause is a faulty wheel speed sensor.
→ Brakes still work but get fault diagnosed. Avoid relying on ABS in wet conditions until fixed.
🔁
Traction Control / ESC Warning
Check Context
If flashing briefly — normal, traction control is working. If stays on solid — traction control or stability control has been disabled or has a fault. Common on slippery roads or after ABS sensor failure.
→ Briefly on = fine. Stays on solid = get diagnosed. Drive with extra care.
🔵
Tyre Pressure Warning (TPMS)
Check Tyres Now
One or more tyres are significantly under-inflated. Can also indicate a slow puncture. Driving on under-inflated tyres increases fuel consumption and tyre wear, and risks a blowout.
→ Check tyre pressures when cold. Inflate to correct PSI. If pressure drops again quickly, check for a puncture.
🌡️
Engine Temperature (Amber)
Monitor / Get Checked
Engine is running hotter than normal but hasn't reached critical temperature yet. Check coolant level when cold. Could indicate a failing thermostat, coolant leak or early head gasket issue.
→ Check coolant level. If rising or keeps recurring, get it investigated promptly.
🔧
Service Due Warning
Book Service
Vehicle is due for its scheduled service — typically oil and filter change plus inspection. On most cars this appears as a spanner symbol or "SERVICE" message. Not an emergency but don't ignore it long-term.
→ Book a service within the next few weeks. Overdue oil can accelerate engine wear.
🚬
DPF Warning (Diesel Only)
Regenerate / Get Checked
Diesel particulate filter is blocked with soot — common after lots of short journeys. The DPF needs a "regeneration" cycle at motorway speeds to burn off the soot. If ignored, the DPF may need replacing.
→ Take a 20–30 minute motorway drive at 60+ mph to initiate regeneration. If light stays on, get it diagnosed.
🔋
Low Battery (Mild / 12V)
Get Tested
Battery charge or health is low. May appear as a battery symbol, "STOP/START unavailable" message or a general warning. Weak batteries cause all sorts of spurious warning lights.
→ Get battery tested — most garages and Halfords do this free. Replace if below 12.4V or health is poor.
🌊
Low Coolant Level
Top Up / Investigate
Coolant level in the expansion tank has dropped below minimum. A small amount of coolant loss over time is normal but significant or repeated loss indicates a leak — which can lead to overheating.
→ Top up with correct coolant when cold. If level keeps dropping, have it inspected for a leak.
💨
Glow Plug Warning (Diesel)
Get Checked
One or more glow plugs have failed. Glow plugs heat the combustion chamber to aid cold starting on diesel engines. Symptoms include hard starting in cold weather and rough running at low temperatures.
→ Can still drive but get diagnosed. Worsens in cold weather. Usually a straightforward repair.
🔓
Immobiliser / Key Warning
Check Key / Fob
Immobiliser has not disarmed or the key fob battery is low. The car may not start or may cut out. Try the spare key. Often caused by a flat key fob battery — a common and cheap fix.
→ Try spare key. Replace key fob battery (usually CR2032). If problem persists, get it diagnosed.

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Green & Blue Lights — Information Only
💡
Sidelights / Parking Lights On
Information
Confirms your sidelights or parking lights are switched on. Normal operation — no action required unless unexpected.
→ No action needed. Reminder that lights are on.
↩️
Indicator Active
Information
Indicator is currently flashing. If it flashes very fast or doesn't flash at all, a bulb may have blown on that side.
→ Fast flashing = check indicator bulbs on that side.
🔄
Cruise Control Active
Information
Cruise control is set and active. The car will maintain its current speed until cancelled via the brake, clutch or cruise control button.
→ No action needed. Normal operation indicator.
💙
Main Beam / High Beam On
Information
Full beam headlights are active. Remember to dip for oncoming traffic and vehicles ahead. Blue symbol is universal across all makes.
→ No action needed. Dip for other road users.
❄️
Frost / Ice Warning
Drive With Care
Outside temperature has dropped to 4°C or below — ice may be present on the road. Not a fault — a safety reminder to adjust your driving.
→ Reduce speed, increase following distance. Watch for black ice especially on bridges and shaded roads.
♻️
Stop / Start System Active
Information
The engine has been automatically stopped at a junction or in traffic to save fuel. The engine will restart automatically when you release the brake or press the clutch.
→ No action needed. Normal operation of stop/start system.
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