Remove The I/O Board - Lenovo ThinkBook 13s Gen 4 Hardware Maintenance Manual

Figure 19. Disconnect the fan cables and then release the antenna cables
Step 4. Remove four screws and then remove the fans.
Figure 20. Remove the fans
Screw specifications
M2 x L4
Go to https://support.lenovo.com/partslookup
part:
Fans

Remove the I/O board

Make sure the following FRU (or CRU) has been removed.
"Remove the lower case" on page 28
Number of screws
4
to look up the Lenovo part number of the following replacement
.
Chapter 4 Removing a FRU or CRU
37