Hmmmmm...i was hoping it was used as the activity LED connection. Thxs for the info.I don't know, but it could be the Tx and Rx pins of a UART (terminal) port. These are commonly used for diagnostic purposes.
Another possibility is a shorting link for "safe mode". This allows the drive to power up in a special test mode. I suspect that the two pins are connected to the two test points at the middle RH edge of the first photo (to the left of "E3").
https://sep.yimg.com/ay/yhst-14437584971410/91711039-6.gif
https://sep.yimg.com/ay/yhst-144375...7-1tb-3-5-sata-hitachi-circuit-board-fw-4.gif