The engine warning light is always alarming. Yet it does not always mean a serious fault. Knowing how to read it saves you an unnecessary expense or, on the contrary, a wrecked engine.
Steady amber: don’t panic, but don’t wait
The engine control unit has detected a fault, usually related to emissions control or combustion: a sensor, the ignition, a fuel cap not closed properly… The car is generally still usable, but book an appointment quickly. Driving for weeks with this light on can make the problem worse and increase fuel consumption.
Flashing amber: ease off
A flashing engine light often signals misfires that can damage the catalytic converter. Slow down, avoid hard acceleration and have the car checked as soon as possible.
Red light: stop
A red light, particularly for oil pressure or engine temperature, signals a risk of serious engine damage. Stop as soon as it is safe to do so, switch off the engine, and check the owner’s manual or call for assistance. Do not restart before you understand the cause: a few kilometres without oil or while overheating is enough to destroy an engine.
Reading the fault code
When the light comes on, the control unit stores a standardised fault code, for example P0301 for a misfire on cylinder 1. A reader plugged into the diagnostic socket (OBD), often under the steering wheel, lets you read it. The code points the diagnosis in the right direction, it does not replace it: the same code can have several causes.
Common false alarms
- A loosely screwed fuel cap can trigger the light on some models: tighten it, and the light may go out after a few journeys.
- A weak battery can bring up spurious electronic faults.
- After a service, a service indicator that stays on has sometimes simply not been reset.
Keep a record
Note the date, the mileage, the colour of the light and the code you read in your maintenance log: this history is a great help to the mechanic, especially if the fault comes back.
