Which of the following is a part of the OBD II test process?

The OBD II test process includes the use of a scan tool, which is an essential component for diagnosing a vehicle's emissions system. The On-Board Diagnostics II (OBD II) is a standardized system that monitors the performance of components critical to emissions control.

Using a scan tool allows technicians to access data from the vehicle's onboard computer system. This includes retrieving diagnostic trouble codes (DTCs), checking the readiness status of emission-related systems, and viewing real-time data on engine performance and emissions control functions. The ability to read these codes and data is crucial for understanding whether the vehicle meets emissions standards, identifying any issues, and determining the necessary repairs.

While the other options, such as idle speed measurement, visual emissions check, and tailpipe emissions sampling, may be part of various vehicle inspections or tests, they are not specifically elements of the OBD II process. In contrast, scan tool usage is directly tied to the OBD II testing methodology and emission evaluations, making it the correct choice in the context of this question.