Car dashboard warning lights, explained

Dashboard lights follow a traffic-light system. Red means a serious safety or mechanical problem — stop driving as soon as it's safe and investigate before continuing. Amber (orange) means something needs attention soon: the car is usually driveable, but a fault is logged and ignoring it tends to make it more expensive. Green and blue lights are just information — headlights on, cruise control active — and need no action. The one to treat with red-level urgency despite its colour is a flashing amber engine light, which signals an active misfire.

Three red lights mean stop as soon as it's safely possible: the oil pressure light (the dripping oil can — the engine can destroy itself in minutes), the coolant temperature light (a thermometer in waves — overheating risks a head gasket), and the brake warning light if it stays on with the handbrake fully released, because it can signal low brake fluid from a leak. A flashing engine management light isn't a stop-the-car light, but it does mean slow right down and get to a garage urgently, because an active misfire can destroy the catalytic converter.

If it's solid amber and the car feels normal — yes, short journeys are generally fine, but book a diagnostic check soon. The fault code stored in the engine computer tells a garage exactly where to start, and problems caught early are usually cheaper. If the light is flashing, the engine is actively misfiring and unburnt fuel is reaching the catalytic converter, which can turn a cheap fix into a £300–£1,000+ catalyst replacement — slow down, avoid hard acceleration, and get it seen urgently. Remember the light itself is an MOT failure while illuminated.

Several will. Since May 2018, an illuminated engine management light, ABS light, ESC/traction control fault light, airbag light, brake fluid warning light, or electric power steering light is a major defect — an automatic MOT fail even if the car drives perfectly. The tyre pressure monitoring light fails cars first used from 1 January 2012. Warning lights are also part of why 'lamps, reflectors and electrical equipment' is among the most common UK failure categories, so get lights investigated before the test, not after.

Amber means the car has detected a fault or a condition that needs attention soon, but not an immediate emergency — you can normally finish your journey. Common examples are the engine management light, ABS, tyre pressure, DPF and AdBlue warnings. The sensible response is to check the handbook, deal with anything you can yourself (tyre pressures, AdBlue top-up, a motorway run for a DPF), and book a diagnostic check for anything that stays lit. Amber lights left ignored have a habit of becoming red lights or MOT failures.

The fault was intermittent — a sensor briefly reading out of range, a damp connector, or a one-off misfire. The light going out doesn't erase the event: the engine computer stores the fault code, and a garage (or a cheap OBD reader) can still read it afterwards. If it was a red light, get it checked regardless. If an amber light comes and goes repeatedly, treat it as a fault that's developing — intermittent faults are cheapest to fix while they're still intermittent.

Start with your handbook — every symbol is listed with the maker's exact meaning, and symbols vary slightly between brands. For an instant plain-English answer, describe the light to CarOkay's free AI diagnosis (or photograph your dashboard and upload it): it identifies the light, explains the likely causes for your specific car using its MOT history, gives an urgency rating, and estimates what a fix typically costs in the UK — so you walk into the garage knowing what to ask.