A method for self-diagnosing remote I/O enclosures with enhanced FRU callouts. When a failure is detected on a RIO drawer, a data processing system uses the bulk power controller to provide an alternate path, rather than using the existing RIO links, to access registers on the I/O drawers. The system logs onto the bulk power controller, which provides a communications path between the data processing system and the RIO drawer. The communications path allows the data processing system to read all of the registers on the I/O drawer. The register information in the I/O drawer is then analyzed to diagnose the I/O failure. Based on the register information, the data processing system identifies a field replacement unit to repair the I/O failure.