Warning lights
Flashing engine warning light: what it means and what to do
A flashing engine warning light signals severe misfires: unburnt fuel reaches the exhaust and can overheat and damage the catalytic converter within a short time. Slow down, avoid hard acceleration and stop as soon as it is safe.
Stop as soon as it is safeWarning lights
Reviewed by Daniel Morales, founder of Reprorace SL, on
Is it serious? Can I keep driving?
Do not keep driving. It is the most urgent message the engine light can give. If you keep driving, the catalytic converter can overheat and fail, and the car may cut out on the move. If the flashing does not stop when you ease off, do not carry on: call a tow truck.
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
- Spark plugs or ignition coils: on gasoline engines, a failing coil or a worn plug leaves a cylinder without a spark. This is the most common cause.
- Injectors: a clogged, leaking or dead injector upsets the mixture of one cylinder.
- Very lean mixture: an air leak or low fuel pressure stops the mixture from burning properly.
- Wiring or connectors: a loose or damaged connector on a coil or an injector cuts the signal on and off.
- Mechanical fault: less common: low compression from valves, piston rings or the head gasket.
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: What are engine misfires (P0300)? What is a catalytic converter and why does it fail? What does a pending, stored or permanent code mean?
Car system: Ignition
What you can check yourself
Note when it flashes: under acceleration, uphill or at idle. Write it down for the garage.
See whether any other light comes on and whether the engine shakes or loses power.
With the engine off and cold, look for any loose connector or hose in plain sight. Do not take anything apart.
Read the fault codes before clearing anything: they show whether the misfire is random or in one cylinder.
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
- P0300Random or multiple cylinder misfire detected
- P0301Cylinder 1: misfire detected
- P0302Cylinder 2: misfire detected
- P0303Cylinder 3: misfire detected
- P0304Cylinder 4: misfire detected
- P0351Ignition coil A, primary control circuit open
- P0420Catalyst system (bank 1): efficiency below threshold
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: misfire counts per cylinder (if the car reports them), fuel trims, engine speed and load.
Frequently asked questions
What is the difference between a steady and a flashing engine light?
A steady light means a fault worth checking soon but rarely immediate. Flashing is the alarm level: misfires that can damage the catalytic converter while you drive.
Can I drive home if it is close?
Only if the flashing stops when you lift off and you drive very gently. If it keeps flashing, the engine shakes or you smell burning, stop and call for assistance: the catalytic converter can fail within a few miles.
Does the code tell me which cylinder is misfiring?
Usually yes: codes P0301 to P0308 point to cylinders 1 to 8, and P0300 means random or multiple misfires. Cylinder numbering depends on the engine.
Can I just change the spark plugs?
Sometimes, but not always: if the cause is a coil, an injector or an air leak, the misfire will come back. Read the code and confirm the cause before replacing parts.
Keep reading
- Engine ignition: how it works and what fails
- Engine warning light on and steady: what it means and what to do
- Car jerks when accelerating: causes and what to do
- Rough idle: why the engine shakes or hunts when stationary
- 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