Which system would allow diagnostics by showing irregular sensor codes numerically?

The choice of the YDIS diagnostics system is appropriate because it is specifically designed for Yamaha products, allowing technicians to diagnose issues by retrieving and displaying error codes linked to various sensors in a numeric format. YDIS stands for Yamaha Diagnostic Information System, and it streamlines the troubleshooting process by providing detailed diagnostic data, including sensor codes that can be critical in identifying irregularities and assessing vehicle performance.

The OBD-II system is commonly utilized across many vehicles for diagnostic purposes, providing a standard interface that produces similar sensor codes, but it is not Yamaha-specific. While it might offer numeric error codes as well, the YDIS is tailored for Yamaha models, making it more effective for those particular vehicles.

The EGR system refers to the Exhaust Gas Recirculation system, which is focused on reducing emissions rather than providing a diagnostic function. Onboard computer diagnostics can also include various systems that monitor vehicle performance metrics but does not uniquely identify itself as a system for displaying diagnostic codes succinctly for Yamaha applications. Therefore, the YDIS system is the most fitting option for providing numeric diagnostic codes for irregular sensor readings in Yamaha vehicles.