A vehicle's OBD-II connector shows no scan tool communication. Upon inspection, you find no voltage at Pin 16. What is the most likely cause?

The situation described involves an OBD-II connector that is not showing any communication due to a lack of voltage at Pin 16. Pin 16 of the OBD-II connector is typically used to supply battery voltage to the scan tool, allowing it to communicate with the vehicle's engine computer.

When there is no voltage present at this pin, one of the most common causes is a blown fuse in the vehicle's fuse box. If the fuse that supplies power to the OBD-II connector is blown, then there won’t be any voltage available for communication. This makes it impossible for the scan tool to establish a connection with the vehicle's onboard systems, explaining the lack of communication.

In contrast, while a broken wire in the harness or a malfunctioning OBD-II connector might also lead to communication issues, these scenarios are less common than a blown fuse. A dead battery could cause similar issues, but it would generally indicate other broader electrical problems, as a dead battery would affect multiple systems in the vehicle rather than just the OBD-II connectivity.

Therefore, identifying a blown fuse is a logical and likely cause of the problem when there is no voltage at Pin 16, enabling the technician to troubleshoot the issue effectively.