Warning lights
Bulb failure or lighting warning light on: what to do
The bulb failure light warns that an exterior lamp has burned out or that the control unit sees abnormal current in its circuit. It is usually a bulb, but it can also be a connector, a ground or an LED lamp the car does not recognize.
Check without hurryWarning lights
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Usually not urgent, but do not ignore it. You can drive if you can see and be seen well, but fix it soon: driving with a light out can get you a ticket and fails the inspection. If the brake lights or headlights are out, do not drive at night.
A careful, general answer: only someone who inspects the car can say whether it is safe to drive. When in doubt, stop somewhere safe and call for assistance.
Most likely causes
- Burned-out bulb: the most common: brake, parking, turn signal, license plate or low beam.
- Connector or bulb socket: moisture and heat corrode the contacts.
- Non-approved or different LED lamp: draws less current and the car reads it as burned out.
- Ground or wiring: especially in the tailgate lights, because of the movement.
- Lighting module: less common: the body control unit or the headlight unit.
Listed from more to less common in general; on your car they may be different. A fault-code reading and a check at the garage confirm which one it is.
To understand it better: Can I diagnose my car myself? What do U codes and lost communication (U0100) mean?
Car system: Electrical system and battery
What you can check yourself
With the car parked, switch on the lights, turn signals and reverse and walk around it; for the brake lights, ask someone to help or look at the reflection on a wall.
If a turn signal flashes faster than normal, there is usually a bulb out on that side.
Replace the bulb with one of the type and wattage given in the owner's manual.
Safe checks only: with the engine off and cold whenever you look under the hood, without taking anything apart and without touching hot or moving parts.
Related fault codes
Generic codes that often come with this symptom. Seeing one does not confirm the cause: it is where the diagnosis starts.
How the ECO-LITE helps diagnose it
Plugged into the OBD socket, the ECO-LITE reads the fault codes of the control units that answer, with the freeze-frame data captured when the fault happened, and shows live data on your phone or computer. With your permission, your garage can see them remotely before you bring the car in.
What to look at here: codes from the body or lighting control unit and battery voltage, if the warning comes and goes.
Frequently asked questions
Why is the light still on with a new bulb?
The lamp may not be the right type, may make poor contact or the fault may be in the socket or the ground.
Can I fit LED lamps?
Only ones approved for your headlight or tail light. Others can trigger a fault warning and may not be legal.
Can I get a ticket for a light out?
Yes, in many countries it is an offense and a defect at the inspection. Carry spare bulbs if your car takes them.
Keep reading
- Electrical system and battery: how it works and what fails
- Car lights flicker or dim: what is going on
- Battery warning light on: what it means and what to do
- Seat belt light will not go off: what it could be
- Car symptoms: what they mean and what to do
- Check engine light on: what to do
- How to read and clear your car's fault codes
- OBD fault codes: what each one means