What does a "check engine" light indicate?

The "check engine" light is a warning signal that indicates the vehicle's onboard diagnostics system has detected a problem in the emissions or performance systems. This light can illuminate for a variety of reasons, including issues with the engine’s functioning, transmission malfunctions, or faults in the fuel or emission systems. The onboard diagnostic system continually monitors various components of the vehicle; when it identifies a fault, it triggers the check engine light to alert the driver that immediate attention may be required.

Understanding the specific nature of the issue often requires a diagnostic scan tool, which can retrieve trouble codes stored in the vehicle’s computer system. These codes can guide technicians to the underlying problem, ensuring that the vehicle remains compliant with emissions regulations and operates efficiently. Thus, when the check engine light comes on, it is important to have the vehicle diagnosed promptly to avoid further damage or costly repairs.