If you have V8 4wd, then: ATRAC works on all the wheels all the time, as does VSC (stability control). When you lock the center diff, then VSC turns OFF.
If you have V6 4wd, then: ATRAC works on all the wheels all the time when you are in 4wd. If you're in 2wd mode, then it only works on the rear axle. When you lock the center diff in 4wd, then ATRAC is still there on all wheels but VSC turns OFF.
Hope this helps.