Car Dashboard Warning Lights Explained — What Each Symbol Means
A warning light on your dashboard can feel alarming — but most of them are giving you useful information, not a crisis. Understanding what each colour and symbol means is the first step to handling it correctly. This guide covers the most common warning lights, what they mean, and what you should do.
The colour system — the most important thing to know
All dashboard warning lights use a universal colour-coding system:
- Red — stop as soon as it is safe to do so. A red warning light indicates a serious, potentially dangerous problem. Do not continue driving until it has been investigated.
- Amber / yellow — do not ignore it, but you can usually complete your journey. Get it checked by a mechanic as soon as possible.
- Green / blue — informational only. These confirm that a system is active (headlights, cruise control, indicators). No action needed.
Red warning lights — stop and investigate
Engine temperature (overheating)
A red thermometer symbol means your engine is overheating. Stop safely and switch the engine off. Do not open the bonnet immediately — let the engine cool for at least 15 minutes. Continuing to drive an overheating engine can cause severe and expensive damage, including head gasket failure. Check the coolant level once cool, and if you're unsure, call for assistance.
Oil pressure warning
An oil can symbol (usually red) means your engine has lost oil pressure. This is serious — pull over and stop the engine as soon as possible. Low oil pressure can destroy an engine within minutes. Check the oil level on the dipstick. If it is low, top up and check for leaks before restarting. If the oil level is fine but the light stays on, do not drive — have the car recovered.
Battery / charging system
A red battery symbol means the car's electrical system is not charging correctly. This could be a faulty alternator, a loose belt, or a failing battery. The car may still run for a while on battery power, but it will eventually lose all electrical systems (including power steering and brakes on some modern cars). Finish your journey if close by, but get it checked the same day.
Brake system warning
A red exclamation mark inside a circle — or the word BRAKE — can mean several things: the handbrake is on (check first), brake fluid is low, or there is a fault in the brake system. If the handbrake is fully released and the light stays on, do not drive until it has been inspected. Brakes are safety-critical.
Power steering warning
A red steering wheel symbol (sometimes with an exclamation mark) means the power steering system has a fault. The car can still be steered, but it will feel very heavy — particularly at low speed and when parking. Avoid high-speed manoeuvres and get it checked promptly.
Amber warning lights — get it checked soon
Engine warning light (check engine)
An amber engine outline — sometimes called the check engine light or malfunction indicator lamp (MIL) — is one of the most common and most misunderstood warning lights. It does not point to a single fault; it means the engine management system has detected something outside of normal parameters.
Common causes include a faulty oxygen sensor, a loose fuel cap, issues with the catalytic converter, or problems with the ignition system. A car diagnostic test will read the stored fault codes and identify the source. Do not ignore a solid amber engine light for weeks — it can mask other faults and may cause an MOT failure.
If the engine light is flashing, treat it as urgent — this typically indicates a misfire that can damage the catalytic converter. Reduce speed, avoid heavy acceleration and get it checked immediately.
Tyre pressure (TPMS)
A flat tyre symbol with an exclamation mark means the Tyre Pressure Monitoring System has detected low pressure in one or more tyres. Check all four tyres and inflate to the correct PSI (found on a sticker inside the driver's door or in your handbook). See our guide on how to check tyre pressure for step-by-step instructions. If you inflate the tyres and the light stays on, there may be a sensor fault or a slow puncture.
ABS warning
An amber ABS light means the Anti-lock Braking System has a fault. Your normal brakes will still work, but the ABS — which prevents wheel lock-up during emergency stops — may not operate correctly. Drive with extra caution and get it investigated. ABS faults will also cause an MOT failure.
Airbag / SRS warning
An amber person-with-airbag symbol means there is a fault in the Supplemental Restraint System. In a collision, the airbags may not deploy — or could deploy unexpectedly. This will cause an MOT failure and should be addressed promptly.
Diesel particulate filter (DPF)
Diesel cars built after 2009 have a DPF that traps soot particles from the exhaust. If you primarily do short, low-speed journeys, the filter can become blocked. The warning light (usually resembling a box with dots) means the filter needs to regenerate. Try a sustained motorway drive at 50–60mph for 20–30 minutes to allow the filter to burn off the soot. If the light remains, a forced regeneration at a garage may be needed.
Service due
An amber spanner or the word SERVICE means your car is due for a scheduled service based on mileage or time since the last service. It is not urgent in the immediate sense, but do not leave it more than a few weeks. See our guide on signs your car needs a service.
Green and blue lights — information only
These lights confirm something is on or active:
- Green indicator flash — indicators or hazard lights are active
- Green headlight symbol — dipped headlights on
- Blue headlight symbol — full beam (main beam) on
- Green cruise control — cruise control is engaged
- Blue frost / snowflake — outside temperature is near or below freezing
If an indicator light flashes faster than usual, one of the bulbs has likely failed.
Key rule: An amber light ignored for long enough often becomes a red light. Deal with amber warnings within a few days — not a few months.
What to do when a warning light comes on
- Note the colour. Red = stop. Amber = monitor and act within days.
- Check the obvious first. Handbrake down? Fuel low? Fuel cap on properly?
- Check your handbook. Every car has a reference section for warning lights — the symbol may be specific to your model.
- Book a diagnostic. If you cannot identify the cause, a diagnostic test at a garage will pinpoint the fault within 30–60 minutes.
Dashboard light on in Ashford TW15?
Bring your car to our Feltham Road garage. We can carry out a diagnostic test to read the fault codes and tell you exactly what the light means — no guesswork, no unnecessary work.