What does the “Check Engine” light indicate during emissions testing?

The “Check Engine” light is an important indicator in vehicle diagnostics, particularly concerning emissions systems. When this light is activated, it signifies that the vehicle's onboard diagnostic system has detected an issue that may affect the vehicle's emissions. This can involve malfunctions in various components integral to the emissions system, such as the catalytic converter, oxygen sensors, or fuel injection system.

During emissions testing, if the “Check Engine” light is illuminated, it can lead to a failure of the emissions inspection. This is because it suggests that the vehicle may not be compliant with emissions standards, which are designed to minimize the environmental impact of exhaust emissions. To resolve the issue, the vehicle should be inspected and any underlying problems addressed before retesting for emissions compliance.