Dashboard warning lights are your car's way of alerting you to a problem — but knowing which ones require immediate action and which can wait until your next garage visit is not always obvious. This guide explains the most common warning lights found in UK cars, what they mean, and what to do when they come on.
Red Warning Lights: Stop the Car
Red warning lights indicate a serious problem that requires immediate attention. If a red warning light comes on while you are driving, find a safe place to pull over as soon as possible and do not continue driving until the issue has been investigated.
- Oil pressure warning (red oil can symbol): Indicates critically low oil pressure. Stop the engine immediately — continuing to drive can cause catastrophic engine damage within minutes. Check the oil level; if it is fine, do not restart the car and call for assistance.
- Engine temperature warning (red thermometer in water): The engine is overheating. Stop safely, switch off the engine, and wait for it to cool before opening the bonnet. Never remove the coolant cap when the engine is hot.
- Battery warning (red battery symbol): The charging system is not working correctly. The car may continue to run for a short period on battery power alone, but drive to the nearest garage or pull over before the battery is fully drained.
- Brake warning (red exclamation mark in circle): Check the handbrake is fully released. If the handbrake is down and the light remains on, it may indicate low brake fluid — do not drive until inspected.
Amber Warning Lights: Investigate Soon
Amber warning lights indicate a fault or condition that does not require you to stop immediately but should be investigated at a garage as soon as is practical — ideally within a day or two.
- Engine management light / check engine light (amber engine outline): One of the most common and least specific lights. It can indicate anything from a loose fuel cap to a sensor fault or emissions issue. The car is usually safe to drive short distances to a garage for a diagnostic check.
- Tyre pressure monitoring system (TPMS — amber tyre cross-section with exclamation mark): One or more tyres is significantly under-inflated. Check and adjust tyre pressures when it is safe to do so.
- DPF warning (diesel particulate filter): The diesel particulate filter is becoming blocked. This can often be resolved by a sustained motorway drive to regenerate the filter, but if the light persists, a garage visit is required.
- Service due (spanner or wrench symbol): A reminder that a scheduled service is due. Not urgent, but book your service soon.
The Engine Management Light in Detail
The engine management light (EML) is the most commonly misunderstood warning light. It is triggered when the engine control unit (ECU) detects a fault and stores a diagnostic trouble code (DTC). The light itself tells you nothing specific — only a garage with a diagnostic tool can read the stored codes and identify the underlying fault.
Common causes of the EML include: a faulty oxygen sensor, a loose or damaged fuel cap, a failing catalytic converter, a faulty mass airflow sensor, or a misfire. Some of these are minor and inexpensive to fix; others can be more significant. As a rule, if the EML is on but the car is running normally and there are no other warning lights, it is usually safe to drive to a garage for a diagnostic check. If the EML is flashing (rather than illuminated steadily), pull over safely — a flashing EML typically indicates a serious misfire that can damage the catalytic converter.
Green and Blue Lights: Information, Not Warnings
Not all dashboard lights indicate a problem. Green and blue lights are generally informational:
- Green indicators (flashing arrows): Confirm that the turn signals are operating.
- Blue headlight symbol: Full beam (main beam) headlights are active.
- Green light symbol: Sidelights or dipped headlights are switched on.
- Green cruise control symbol: Cruise control is engaged.
If you are unsure about any warning light on your specific vehicle, consult your owner's manual — every model uses slightly different symbols and colours, and the manual will give you the exact meaning for your car.