Jörgen Nilsson have a great post here on how to do the BIOS to UEFI switch on one task sequence in SCCM. There was a couple times during his guide where I had to try different things before I could get it to work. So that is why I made this post.
All the credit goes of course to Jörgen Nilsson!
x1. Download copy.cmd
x2. Download TSEnv2-18.104.22.168 from 1E (http://info.1e.com/website-freetools-1e-tsenv2)
1. Localize your “\\SERVER\DRIVE$\Microsoft Configuration Manager\OSD\bin”.
2. Copy the corresponding version of TSEnv2.exe to the x64 as well as the i386 subfolder.