What does the "Check Engine" light indicate in emissions testing?

The "Check Engine" light serves as an important indicator for vehicle owners, particularly regarding the emissions control system. When this light illuminates, it signals that there is a malfunction somewhere in that system, which could potentially lead to increased emissions. This could be due to various issues, such as a faulty oxygen sensor, a problem with the catalytic converter, or a leak in the fuel system, among others. Identifying and addressing these malfunctions is crucial for ensuring that the vehicle complies with emissions regulations and operates efficiently.

In contrast, while a properly functioning vehicle should ideally not have the "Check Engine" light on, this light does not indicate normal vehicle function. It is designed specifically to alert drivers of issues that need investigation. The light also does not serve as a reminder for routine maintenance needs or indicate a low fuel level—those aspects are typically monitored through other dashboard indicators specific to those purposes. Understanding the function of the "Check Engine" light is essential for maintaining both vehicle performance and environmental compliance.