What does the OBD system monitor in a vehicle?

The On-Board Diagnostics (OBD) system is an essential component in modern vehicles, primarily focused on monitoring the engine performance and emissions control systems. It provides real-time data about the functionality of various engine and emissions components, ensuring that they operate within specified limits. The OBD system is designed to detect malfunctions and issues that could result in excessive emissions, alerting the driver through warning lights and error codes.

By keeping tabs on critical components, such as the catalytic converter, oxygen sensors, and fuel injection systems, the OBD system plays a crucial role in maintaining compliance with environmental regulations, aiding in emissions testing, and facilitating vehicle diagnostics during maintenance and repair. Thus, it is specifically tasked with oversight of the engine and emissions control systems, making this the accurate choice.

The other options pertain to different functions in a vehicle. Tire pressure monitoring systems track the health of the tires, fuel consumption data is typically monitored separately, and battery status is often managed by the vehicle's electrical system. These areas are not covered by the OBD system, highlighting its specific focus on engine performance and emissions controls.