Solid or flashing
A solid light means a fault has been logged and should be checked soon. A flashing light usually means an active misfire, which can overheat and damage the catalytic converter. If it is flashing, reduce load, avoid hard acceleration and get it checked promptly.
Easy things first
A loose fuel cap can trigger an evaporative system fault on some vehicles. Tighten it and see if the light clears after a few drives. If the car is running differently (rough idle, hesitation, loss of power, unusual smell), do not wait for the light to clear.
Why a code is not a diagnosis
A scan tool reads fault codes, and the code points to a system or circuit, not necessarily a failed part. An oxygen sensor code, for example, can be caused by a vacuum leak or wiring. Good diagnosis means testing to confirm before replacing parts.
What to tell the mechanic
Whether the light is solid or flashing, when it came on, any change in how the car drives, any codes you already have from a scan, and recent work done on the car.
Safe to drive?
Solid light and the car drives normally: usually fine to drive to a booking soon. Flashing light, overheating, oil pressure warning or loss of power: stop driving and arrange inspection.
General guidance only, not a diagnosis. If in doubt, do not drive it and have it inspected. In an emergency, call 111.
Who can help
Get quotes for car diagnostics near you
Questions
Will the check engine light fail a WOF?
Warning lights that indicate a fault in a safety system can be a reason for rejection. Get the cause found and fixed before the inspection.
Can I just clear the code?
Clearing it hides the symptom. If the fault is real, it will come back.