The check engine light is the car telling you that the computer found something outside its normal range. It does not say what, only that a code has been stored.
Steady or flashing?
- Steady light. A fault has been detected. The car is usually safe to drive for a short time, but you should have it scanned soon.
- Flashing light. This usually means a serious problem such as a misfire. Reduce speed, avoid heavy acceleration and stop as soon as it is safe.
Common reasons the light comes on
- A loose or faulty fuel cap.
- A faulty oxygen sensor.
- Worn spark plugs or ignition coils.
- A mass airflow sensor problem.
- A fault in the emissions system.
- Electrical faults such as a poor connection to a sensor.
Notice how the car behaves
- Rough running, loss of power or poor fuel economy.
- Strange smells or smoke.
- Overheating or other warning lights at the same time.
The right next step
A diagnostic scan reads the stored code and points to the area of the fault. It does not name the broken part by itself, so a technician then tests the circuit to confirm. Clearing the light without fixing the cause only makes it return.