Check engine light: what it means and what to do
The check engine light (an engine-block outline, usually amber) means the engine management system has stored a fault code. Steady means investigate soon; flashing means stop driving.
Investigate soon — a system is degraded
Steady amber: book a diagnostic scan within a few days. Flashing: pull over safely and stop driving — a misfire can destroy the catalytic converter within minutes.
Usually yes for short, gentle journeys if the light is steady and the car drives normally. Do not keep driving if it is flashing, or if you notice loss of power, rough running, smoke or unusual noises.
Common causes
- Loose, damaged or missing fuel filler cap breaking the evaporative-emissions seal
- Failing oxygen (lambda) or mass-airflow sensor reporting out-of-range values
- Worn spark plugs or ignition coils causing a misfire
- Catalytic converter efficiency below threshold
- Vacuum or intake leak after the airflow sensor
What to do next
- 1Check whether the light is steady or flashing — that alone decides the urgency.
- 2If steady, check the fuel filler cap is tight; a loose cap is a genuinely common trigger.
- 3Note any change in how the car drives: power, idle, fuel use, smells or noises.
- 4Have the fault codes read. A code is a starting point, not a diagnosis — it names the circuit, not the failed part.
- 5Log the event and the repair against the vehicle so the pattern is visible if it returns.
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Ask the AI mechanicFrequently asked
- Will the check engine light clear itself?
- Sometimes. If the underlying condition stops recurring — a re-tightened fuel cap, for example — most systems clear the lamp after a number of successful drive cycles. The stored code usually remains readable.
- Is it safe to just clear the code?
- Clearing a code without fixing the cause only hides the symptom, and it also erases the freeze-frame data a technician needs. It will return once the fault is detected again.
General guidance only. Symbols and thresholds vary between manufacturers — always confirm against your vehicle's owner manual, and treat any red lamp as a reason to stop.
Other dashboard lights
- Oil pressureThe red oil-can symbol means the engine has lost oil pressure. This is the most serious light on the dashboard — continued driving can destroy the engine in under a minute.
- ABSThe amber ABS lamp means the anti-lock braking system has disabled itself. Normal braking still works, but the wheels can lock under hard or emergency braking.
- Brake systemThe red brake light (an exclamation mark inside a circle) covers three very different things: the parking brake being applied, low brake fluid, or a hydraulic circuit fault.
- Battery / chargingThe red battery symbol means the charging system is no longer supplying enough voltage. The car is running on stored battery charge and will eventually stop.
- Coolant temperatureA red thermometer symbol means the engine is overheating. Continued driving risks a warped head, failed head gasket or a seized engine.
- Tyre pressure (TPMS)The amber horseshoe with an exclamation mark means at least one tyre is significantly below its target pressure — or the monitoring system itself has a fault.
- Airbag / SRSThe SRS or airbag symbol means the supplementary restraint system has detected a fault and has disabled itself. In a crash, the airbags or pretensioners may not fire.
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