What is the role of the On-Board Diagnostics (OBD) system in emissions testing?

The key role of the On-Board Diagnostics (OBD) system in emissions testing is to monitor vehicle performance and emissions systems for any faults. The OBD system continuously assesses the operational status of various engine components and emissions control systems. This monitoring allows for the detection of malfunctions that could lead to increased emissions, ensuring that the vehicle is compliant with environmental regulations. When a fault is detected, the OBD system triggers a warning light on the dashboard and stores diagnostic trouble codes, which can be read by technicians during inspections. This functionality is crucial for maintaining air quality and ensuring that vehicles meet the required emissions standards.

Other options relate to aspects such as fuel efficiency, vehicle speed, or infotainment features, but they do not directly pertain to the primary function of the OBD system in emissions testing.