The check engine light is a general signal that the control unit logged a reading outside the expected range. The cause can be as simple as a loose fuel cap or as serious as a combustion fault.
The practical rule: if the light is steady and the car drives normally, you can drive carefully to the workshop. If it flashes, or comes with vibration or power loss, stop immediately — a flashing light usually means a misfire that can destroy the catalytic converter.
Don’t rely on a cheap OBD reader alone. A fault code points to the affected circuit, not the failed part, and replacing parts based on codes alone is the single biggest source of wasted money in car repair.