The rule of thumb: red means stop and investigate now, amber means something needs attention soon.
The engine is not maintaining oil pressure. This is the most damaging light on the dashboard.
What to do: Stop as soon as it is safe and switch the engine off. Do not carry on to get home — running without oil pressure can destroy an engine in minutes.
The engine is overheating, often from a leak, a failed thermostat or a dead cooling fan.
What to do: Pull over, switch off and let it cool. Never open a hot expansion tank. Driving on risks a warped head or blown gasket.
Low brake fluid, a hydraulic fault, or worn pads on some vehicles. On many cars it also shows when the handbrake is applied.
What to do: If it stays on with the handbrake released, treat it as urgent. Check pedal feel; if it is soft or travelling further than normal, do not drive.
The alternator is not charging. The vehicle is running off battery reserve only.
What to do: Switch off heated screens, aircon and stereo and head somewhere it can be checked. Expect it to stop running once the battery is flat.
The ECU has logged a fault. Very common causes are sensor faults, misfires, EGR or emissions issues.
What to do: Usually safe to drive gently, but get the codes read. Ignoring it can turn a cheap sensor into an expensive catalytic converter.
An active misfire is dumping unburnt fuel into the exhaust. This is a different, more serious situation to a steady light.
What to do: Reduce speed and load and get it looked at immediately. Continued driving commonly destroys the catalytic converter.
The anti-lock braking system has faulted, often a wheel speed sensor.
What to do: Normal braking still works, but ABS may not intervene in an emergency stop. It is also an MOT failure item, so book it in.
One or more tyres has lost pressure, or the system needs resetting after a tyre change.
What to do: Check all pressures cold against the door-frame or filler-flap figures. A slow puncture that gets ignored becomes a blowout.
The filter is clogging, usually after a lot of short, cold journeys that never allow it to regenerate.
What to do: A sustained run at higher revs on a dual carriageway often clears it. Repeated ignoring leads to a forced regeneration or filter replacement.
A fault in the restraint system — often a seat or belt connector.
What to do: The vehicle drives normally but the airbags may not deploy. It is an MOT failure item and worth fixing promptly.
Photograph the dashboard and AutoAid will try to identify it, then give likely causes, urgency and an indicative repair cost range.
Photograph the warning lightSymbols vary between manufacturers — your handbook is the definitive guide for your vehicle. Anything safety-critical should be inspected by a qualified mechanic.