What should a technician check next when a scan tool shows no power at the vehicle's OBD-II port but grounding is good?

When a scan tool indicates that there is no power at the vehicle's OBD-II port but confirms that grounding is good, the next logical step is to check for power specifically at pin 16 of the OBD-II connector. Pin 16 is designated as the power supply pin, which provides the necessary voltage to the scan tool for its operation. If there is no voltage at this pin, it confirms that there is indeed a power delivery issue that is preventing the scan tool from functioning, even with good ground established.

Checking the voltage at pin 4, which is typically a chassis ground, would not provide useful information in this scenario as grounding has already been confirmed as good. Evaluating the connection to the PCM is essential for ensuring overall communication, but the immediate concern is verifying that power is reaching the scan tool through the OBD-II connector. Lastly, checking the brown wire continuity might be relevant if specific vehicle wiring issues are suspected, but it would not directly address the immediate issue of verifying power at the OBD-II port. Thus, focusing on power at pin 16 directly addresses the problem of the scan tool being inoperable due to no power supply.