What is the role of the ECU in modern vehicles?

The role of the Engine Control Unit (ECU) in modern vehicles is fundamental because it is responsible for controlling engine performance and diagnostics. The ECU utilizes various sensors to monitor parameters such as air-fuel mixture, engine temperature, and ignition timing. By processing this data, it can make real-time adjustments to the engine’s operation, ensuring optimal performance, efficiency, and emissions compliance.

Additionally, the ECU also enables onboard diagnostics, which allows it to identify issues within the engine and associated systems. This diagnostic capability is crucial for troubleshooting problems and maintaining the vehicle's overall health. By managing the engine's functions, the ECU plays a central role in enhancing drivability and reliability, making option B the most comprehensive and accurate representation of its primary function.

Options focused on narrower or unrelated aspects, like managing just electrical systems, enhancing fuel economy, or regulating tire pressure, do not fully encapsulate the ECU's extensive responsibilities.