Q. Can one climb on Yom Tov or Shabbat on the back of a pick up truck where he build a Suka when travelling and eat there? Can you open the doors of the truck if the light does not go on? Can one push the truck (when in neutral) to a better location, in a fenced lot?

A. Shulchan Aruch (O.H. 624: 2) rules that one is allowed to build a sukka on top of a “agalah” or carriage as long as it is firm enough to survive an ordinary wind. Mishna Berura (ibid. 10) also mentions to be careful that the sukka should have the right dimensions.
Horav Shlomo Miller’s Shlit’a opinion is that in order to open the doors of the truck on Yom Tov you may have to disconnect the battery of the vehicle since besides the lights some other unseen functions may be triggered by opening the doors in a modern computerized vehicle.
He also maintains that when needed one may push and move this truck to a desired location.

Rabbi A. Bartfeld as advised by Horav Shlomo Miller Shlit”a