The check engine light is an indicator that your car's onboard diagnostics system (OBD) has detected an issue. It could range from a minor problem like a loose gas cap to a more serious issue like engine misfires or emissions system malfunctions.

If the light is steady, it's usually safe to drive for a short period while you schedule a diagnostic check. However, if the light is flashing, it indicates a more serious problem, and you should stop driving immediately to prevent potential damage to your engine.

Some common reasons include a loose or damaged gas cap, faulty oxygen sensors, malfunctioning spark plugs, issues with the catalytic converter, or problems with the mass airflow sensor.

You can reset it by disconnecting the battery or using an OBD-II scanner. However, it's crucial to address the underlying issue causing the light to come on, as simply resetting it without fixing the problem can lead to further damage.

The cost can vary greatly depending on the problem. A diagnostic test usually ranges from $50 to $150. The repair cost will depend on the specific issue, with minor fixes like tightening a gas cap costing little to nothing, while more complex problems like a faulty catalytic converter could cost several hundred dollars or more.