For PCIe Slot 5  second Processor is required. You can refer below link for Processor to PCIe slot mapping [URL] 
I have a T430 with a single processor. I installed a Dell 12Gbps HBA in Slot 5 that is reporting firmware 16.17.00.03. BIOS, iDRAC, lifecycle controller are all up to date. However VMWare 6.7 U3 is not seeing the card. So I ran a clean install of ESXi using the latest build Dell build on the T430 page and still do not see it. I have also tried updating the firmware on the HBA twice via the iDRAC to 16.17.01.00 it reports completed however the firmware remains on 16.17.00.03. I went into the lifecycle controller forced a fresh system inventory and no change. It confirmed it was inventoried and the last update time but no firmware change.  I even tried an upgrade to 16.17.00.05 to see if that worked (a smaller step up) but no change the card will not move from 16.17.00.03. My main problem is seeing it in ESXi I just thought the firmware update might help, as long as it works I don't need the firmware upgrade, although refusing to update after supposedly successful upgrades is quite strange. Anyone have any ideas? Thanks, Kenny
Dell 12Gbps HBA in T430 Can't update Firmware and VMW Doesn't see it