Regarding the new PSU BIST, which statement is true?

The statement indicating that disconnecting the AC power cord for 15 seconds resets the PSU BIST (Power Supply Built-In Self-Test) is correct because this is a standard method for effectively resetting many electrical systems, including power supply units in computer equipment. This action allows the internal components of the power supply to reset, clearing any temporary errors or states that may have been affecting its operation.

In the context of PSU BIST functionality, when you disconnect the power source, the PSU is no longer receiving electrical power, which can clear fault conditions and refresh its operational state. Once the power cord is reconnected after the specified time, the PSU can resume operations fresh, running the self-test again to verify that everything is functioning correctly.

The other statements regarding the PSU BIST do not align with factual practices related to how this functionality typically operates in modern power supply units. While it's essential for the PSU BIST to be correctly reset to function correctly, the methods mentioned in the other options do not accurately describe the PSU BIST's operational characteristics.