The Colors Are the First Message

Before you identify any particular symbol, notice its color. Vehicle manufacturers follow a broadly consistent traffic-light convention, and it tells you most of what you need to know before you’ve worked out what the icon is supposed to be.

  • Red — stop safely as soon as you can. Something is either dangerous or actively destroying itself.
  • Amber or yellow — something needs attention soon. Usually safe to continue driving carefully; don’t leave it for a month.
  • Green or blue — informational. A system is switched on and working: headlights, cruise control, indicators.

When every light on the dash comes on for a couple of seconds as you turn the key and then goes out, that’s the bulb-check self-test, and it’s supposed to happen. What matters is which ones stay lit after the engine starts — and, importantly, if a warning light never comes on during that self-test, someone may have removed the bulb to hide a problem, which is worth knowing on a used car.

The Red Lights That Mean Pull Over Now

Oil pressure — an oil can with a drip. This is not the “you’re due a service” light and it is not the same as low oil level. It means oil is not being pumped at pressure through the engine. Continuing to drive can destroy an engine within minutes, because the moving parts are running metal against metal. Pull over safely, switch off, and check the oil level. If it’s low, topping up may resolve it; if the light stays on with correct oil, the car needs a tow, not a drive to the garage.

Coolant temperature — a thermometer in liquid. The engine is overheating. Pull over, switch off, and let it cool for at least half an hour before touching the cap on the expansion tank — the system is pressurized when hot and opening it can spray scalding coolant. Driving on with an overheating engine warps cylinder heads and blows head gaskets, both of which cost more than most cars are worth.

Brake system. If it isn’t just the handbrake left on, this can mean low brake fluid or a hydraulic fault. Test the pedal gently at low speed; if it feels soft, spongy, or goes further than usual, don’t drive.

Battery or charging system — a rectangular battery icon. Confusingly, this doesn’t mean the battery is flat; it means the alternator isn’t charging it. The car is now running off stored battery power and will progressively lose electrics — first the radio and lights dim, eventually the engine stops. You typically have somewhere from a few minutes to an hour. Head somewhere useful immediately, with lights and air conditioning off.

Airbag / SRS. The car still drives, but the airbags may not deploy in a crash. Get it diagnosed rather than ignored.

The Amber Light Everyone Dreads

The check engine light — an engine block outline, sometimes with the word CHECK — is the most misunderstood indicator on any dashboard, because it covers hundreds of possible fault codes ranging from trivial to serious.

There are two distinct versions:

Steady amber. The engine management system has logged a fault. Common causes range from a loose fuel cap (genuinely — it triggers an evaporative emissions fault on many cars) to a failing oxygen sensor, an ignition coil, or a clogged catalytic converter. The car is generally safe to drive gently, but the fault should be read soon. Fuel economy and emissions are usually affected, and a small unfixed fault can damage the catalytic converter, which is an expensive part.

Flashing. This is a different message entirely. A flashing check engine light typically indicates an active misfire severe enough to be dumping unburnt fuel into the exhaust, where it can overheat and destroy the catalytic converter in a short distance. Reduce speed, avoid heavy acceleration, and get to a garage promptly — or stop and call for recovery if it’s flashing badly.

Any garage, and many parts stores, can read the fault code from the OBD-II port under the dashboard, standard on essentially all cars sold since the early 2000s. An inexpensive Bluetooth reader lets you read the code yourself before any conversation about repairs, which is not the same as diagnosing the fault but does mean you know whether “P0420 catalyst efficiency” is on the table before someone quotes you for it.

The Rest of the Amber Family

Tire pressure monitoring (TPMS) — a horseshoe shape with an exclamation mark, often mistaken for anything but a tire. One or more tires are significantly low. Check all four with a gauge; cold weather alone can drop pressures enough to trigger it, since air contracts as it cools. If it’s flashing rather than steady on startup, the sensor system itself has a fault.

ABS. Normal braking still works; the anti-lock function may not. Fine to drive to a garage, but leave more stopping distance and remember that emergency braking on a wet road is where you’d have wanted it.

Traction control / stability control. If it’s flashing briefly while driving, the system is actively working — that’s normal on a slippery road. If it stays on constantly, the system has disabled itself, often because of a wheel speed sensor, and often alongside the ABS light for the same reason.

Glow plug (diesels) — a coil symbol. During cold starts it’s normal and you wait for it to go out before cranking. Staying lit or flashing while driving indicates a fault.

Diesel particulate filter (DPF). The filter is clogging, usually because the car does mostly short, low-speed trips and never gets hot enough to burn off the soot. Many cars clear this with a sustained drive at higher revs; leaving it can mean an expensive forced regeneration or replacement.

The Two Rules Worth Remembering

First: red means stop, amber means book it. If you remember nothing else and can’t identify the icon, that single distinction prevents most of the catastrophic outcomes.

Second: a warning light that goes off by itself hasn’t necessarily fixed itself. Intermittent faults are still faults, and most cars store the code even after the light clears. If something has appeared twice, get the codes read — the record is still there, and an intermittent electrical fault found early is a far better outcome than the same fault found later on the hard shoulder.

Your owner’s manual has the definitive list of symbols for your specific car, usually in the first twenty pages. It’s worth five minutes with a coffee before you ever need it.