Modern dashboards light up like a fruit machine on start-up and then go out. What is left glowing afterwards is the part that matters, and the single most useful thing to know is that the colour is doing most of the talking.
Red means stop as soon as it is safe to do so. Amber means something has failed or degraded and it needs looking at, but you are usually not about to destroy anything in the next mile. Green and blue are information, not warnings.
That rule covers most of it. Below are the ones where getting it wrong is expensive, and the three that genuinely mean do not drive another mile.
The three you do not drive on
Oil pressure — the red oil can. This is the most expensive light on the car and the one most often mistaken for a service reminder. It does not mean the oil is low; it means the oil is not being pumped at pressure. An engine running without oil pressure destroys its bearings in a very short time, sometimes in under a minute. Pull over as soon as it is safe, switch the engine off, and do not restart it to move it “just a bit further”. Checking the dipstick is worth doing, but a full dipstick with the light on is still a stop.
Temperature — the red thermometer, or a rising gauge. An overheating engine can warp a head or blow a gasket, and continuing to drive is what turns a repair into a replacement. Stop, switch off, and let it cool properly rather than for five minutes. Do not open the expansion tank while it is hot; a pressurised cooling system will scald. Our guide to what to do when a car overheats covers the rest.
Brakes — the red circle with an exclamation mark. If the handbrake is off and this is still lit, treat it as a hydraulic fault until proven otherwise: low fluid, a leak, or a pressure problem. Combined with a pedal that feels soft or travels further than usual, it is a stop-now. There is more in our guide to brake problems and when not to drive.
The red one everyone misreads
The battery or charging light. It is red, and it does not mean the battery is flat. It means the alternator is not charging, so everything in the car is running off the battery alone and there is a finite amount of that.
You are not going to damage the engine, but you are going to stop, probably somewhere worse than where you are now, and probably with no power steering and no lights. Turn off everything you do not need, do not switch the engine off if you can avoid it, and head for somewhere you can safely stop rather than trying to reach home. Our flat battery guide explains how to tell the two apart.
The ambers that matter more than they look
The engine management light, flashing. A steady amber engine light means a fault has been logged and you can generally drive gently to a garage. A flashing one is a different message: it usually indicates a misfire severe enough to damage the catalytic converter, which is not a cheap part. Ease off, avoid load, and get it looked at rather than pressing on. Our guide to limp mode and whether you can drive goes through this properly.
Power steering. On an electric system the assistance can drop out entirely, and a car with no assistance is heavy rather than impossible — but it is a shock at low speed in a car park. Reduce speed and be aware it may not come back.
Tyre pressure monitoring. Often just a pressure drop with the cold weather, sometimes a slow puncture. Check the pressures rather than resetting the light, and look at the tyre.
ABS and traction control. The brakes still work; the anti-lock function may not. That matters most in the wet and on Sheffield’s hills, so drive accordingly and get it read.
Airbag. Nothing will happen while you drive, but the system may not deploy in a collision. It is not an emergency and it is not something to leave for months either.
If you have a red light on and you are not sure, the safe call is to stop. Tell us the colour, the symbol and what the car is doing, and we will tell you honestly whether it is a recovery job or something you can drive gently to a garage. We would rather say that on the phone than charge you for a callout. DK’s Recovery covers Sheffield 24 hours a day on +44 7867 860723.
If the car has already stopped rather than warned you, our guide to what to do first when you break down in Sheffield takes it from there.
What the light does not tell you
A warning light is a symptom, not a diagnosis. The engine light in particular can be triggered by dozens of things, from a loose fuel cap to a failing turbo, and the only way to narrow it is to read the fault code. Any garage can do that in minutes, and plenty of independents will read it for very little.
What the light also does not tell you is how long it has been on. If you have just bought the car, or it has been standing, assume nothing about how long the fault has existed.
Lights that come on together
Several warning lights appearing at once usually points at something electrical rather than several simultaneous failures. A failing alternator, a poor earth or a dying battery can light up half the dashboard. So can a low battery on a car that has stood, which we cover in our guide to bringing a car back after months standing.
The other common cause is a car that has been jump started incorrectly, or one where a battery has been disconnected and reconnected. Some systems need a short drive to relearn and some need resetting properly.
An engine light combined with a sudden, deafening exhaust note is a particular case: see our guide to catalytic converter theft.
And ahead of any warning light, a burning or electrical smell is its own instruction. Our guide to smoke or fire from under the bonnet covers what to do and why you never open it.
Frequently asked questions
What do the different warning light colours mean?
Red means stop as soon as it is safe. Amber means a fault has been detected and the car needs looking at, but you are usually not doing immediate damage. Green and blue are information, such as lights being on, rather than warnings.
Which warning lights mean I must stop immediately?
Oil pressure, engine temperature and the red brake warning light with the handbrake released. Oil pressure is the most urgent: an engine running without oil pressure can destroy its bearings in under a minute.
The red battery light is on. Is my battery flat?
No. That light means the alternator is not charging, so the car is running off the battery and will eventually stop. Turn off anything you do not need, avoid switching the engine off, and get somewhere safe rather than trying to reach home.
Is a flashing engine light worse than a steady one?
Yes. A steady amber engine light means a fault has been logged and you can usually drive gently to a garage. A flashing one usually means a misfire serious enough to damage the catalytic converter, so ease off and stop pressing on.
Can I drive with the ABS light on?
The normal brakes still work, but the anti-lock function may not, which matters most in the wet and on hills. It is not a stop-now light, but it should be read and fixed rather than ignored.
Several lights have come on at once. What does that mean?
Usually one electrical cause rather than several separate failures. A failing alternator, a bad earth or a dying battery can light up much of the dashboard at once, as can an incorrect jump start or a battery that has been disconnected.
