Codes and warning lights
What does a yellow warning light mean compared with a red one?
A red light warns of a serious fault or a safety risk: stop the car as soon as it is safe and do not drive on without knowing what it is. A yellow or amber light points to a fault or a reminder that needs checking soon, and green or blue lights only tell you that something is switched on.
Reviewed by Daniel Morales, founder of Reprorace SL, on
Which red lights mean you must stop?
Oil pressure, engine temperature, brake, battery charge and airbag are the most common. Low oil pressure or overheating can wreck an engine within minutes, and a brake or airbag fault affects your safety.
If one comes on while driving, pull over when you can, turn the engine off if it is the oil or temperature light and check the owner's manual before restarting.
Can I keep driving with a yellow light?
Usually yes, carefully and without long trips, until it is checked: a steady check engine light, the tire pressure light or the service reminder usually give you some time. Change your mind if the car loses power, makes noises or smells odd.
There is one important exception: a flashing check engine light warns of misfires that can damage the catalytic converter. Treat it like a red light: ease off and stop as soon as you can.
Why can the same light show up in two colors?
Some cars use the same symbol in yellow for a reminder and in red for the serious fault: a yellow oil light usually means a low level and a red one, no pressure. The brake light works in a similar way.
The owner's manual explains every symbol for your model. If you do not have it at hand, go by the color and by how the car drives.
General guidance only: every manufacturer and model has its own details. Always follow your vehicle's manual and, if in doubt, ask a workshop.
See what your car is saying
The ECO-LITE reads the codes behind the check engine light and other systems and explains them in your account; with a red light, stop first and read later.
Presale price: €129 · US$129
Frequently asked questions
What does a green or blue light mean?
That something is on, such as the low beams or cruise control. They do not signal a fault.
Is a red light that goes off by itself no longer serious?
Not necessarily: it can come back. Check the level or the cause and have the codes read before a trip.
Does every warning light store a trouble code?
Engine, brake, airbag and many others do; level and service reminders sometimes do not.