Modern cars monitor themselves constantly and report through a panel of small hieroglyphs that most drivers never learned to read. The good news: the system has a built-in priority code. Colour tells you the urgency before you even identify the symbol – and only a handful of lights genuinely mean “stop the car now”. Knowing which ones is worth five minutes of anyone’s time.
The colour code, first
- Red: a safety or serious mechanical issue. Stop when safely possible – sometimes immediately.
- Amber/yellow: attention needed soon. Drive gently, book the garage.
- Green/blue: information only – something is switched on.
The stop-now three
Oil pressure (the red oil can)
This is not a maintenance reminder – it means oil is not circulating under pressure right now. An engine run without oil pressure destroys itself in minutes, not miles. Pull over safely, switch off, check the oil level once things cool. If topping up does not extinguish the light, the car travels on a truck, not on its engine.
Coolant temperature (the red thermometer)
The engine is overheating. Continuing to drive risks a warped head and a gasket failure – four-figure territory. Pull over, switch off, and never open a hot coolant cap: the system is pressurised and will scald you. Low coolant after cooling suggests a leak; no visible loss can mean a failed thermostat or water pump. Either way, this one earns a recovery call, not bravery.
Brake system (red exclamation in a circle)
First check the handbrake is fully released – the innocent cause. If the light stays, it can mean low brake fluid or a hydraulic fault. Brakes are not a “see how it goes” system: if the pedal feels different in any way, stop and get recovered.
The act-soon amber tier
- Check engine light: steady means book a diagnostic this week; flashing means active misfire – slow down and stop soon, or the catalytic converter pays. Our full check-engine guide covers the codes and causes.
- Battery/charging (red but rarely instant): the alternator is not charging – the car is running on battery reserve, which is measured in minutes to an hour. Head home or to a garage directly, skipping errands. See our car battery guide.
- ABS light: normal braking still works; the anti-lock assistance does not. Drive gently to the garage – and treat it urgently in winter.
- Tyre pressure (TPMS): check pressures within the day, not the month – and remember the system alerts late (our tyre guide explains why monthly manual checks still matter).
- Airbag/SRS: the car drives fine, but the systems that save you in a crash may not deploy. Book it promptly.
- DPF (diesels): often cured by a 15-20 minute motorway run that lets the filter regenerate; ignored, it becomes a very expensive amber light.
Habits that make warning lights boring
Glance at the dashboard on every start – all warning lights should illuminate briefly and then go out; one that never lights even at start-up may be a disconnected bulb hiding a fault. Do not clear codes just to make lights disappear, and do not tape over anything (people genuinely do). Most of all, respect the colour code: ambers cost less than reds, and reds cost less than towing a seized engine. The five-minute monthly routine – oil level, coolant level, tyre pressures – prevents the majority of roadside dramas these lights announce.
