Figure 135. Disconnecting 4U PCIe riser power cables
Table 26.  4U PCIe riser power cables
Length From To
1  230 mm (shorter)  PCIe riser cage 2
upper power connector
2  320 mm (longer)  PCIe riser cage 1
lower power connector
2.  If applicable, disconnect M.2 and 7mm drive cables from the system board.
3.  If applicable, disconnect all the flash power module cables. 
250
ThinkSystem SR860 V2 Maintenance Manual