This won’t explain how or why elevators work. This will only show you what was changed in order to prevent them in Modern Warfare 2.
While trying to disable elevators in CoD4, I noticed that if I overjump a call to PM_CorrectAllSolid or PM_JitterPoint in later CoD’s, elevators will stop working.
I couldn’t find anything special in that function and decided to compare it to the one in MW2 … and well, Spot On!
PM_CorrectAllSolid - CoD4
PM_CorrectAllSolid - MW2
All thats needed to re-enable elevators is to nop 1 jump equal instruction and the code-flow will be the same as it was in CoD4 :)