If a vehicle fails a smog check due to a communication error with the scan tool, which OBD-II pin should be checked first for proper power?

In the context of OBD-II communication and the pin configuration of the diagnostic connector, pin 16 is specifically used for providing power to the scan tool. When a vehicle fails a smog check due to a communication error, ensuring that the scan tool receives proper power is essential for maintaining effective communication with the vehicle's onboard diagnostics system.

Checking pin 16 first is crucial because it is sourced directly from the vehicle's battery and serves as the primary power supply for the scan tool. If there is an issue with the power supply at this pin, the scan tool will not operate correctly, leading to communication errors that can prevent accurate smog check evaluations.

The other pins serve different functions, such as grounding or data transmission, and do not serve as the primary power source for the scan tool. Therefore, verifying the power at pin 16 is a logical first step in troubleshooting communication errors experienced during a smog check.