I haven't used mine as its past that time in NC, but I did wonder the same thing and meant to test it. Most vehicles its just the bottom. I am interested to hear the answer as well... or I could step into the garage and test it out.
Isn't that better though.. not sure how good a feature is that only works for a few minutes and then is too uncomfortable and has to be turned off.It does both the bottom and the back, but it doesn't get nearly as hot as GM cars. My wife's Buick gets so hot you can only use it for a few minutes. I've found myself leaving the heated seats and steering wheel on for long periods of time without it getting too hot.
Forgive me, but I don't understand this logic. The heated seats in my Silverado are adjustable and quite warm compared to my wife's Lexus. Yet if it gets too warm, I turn it off and the seat stays warm (real leather?) for quite a while. If it cools off I hit the button again if need be (although I don't think I ever have in this case..) Besides having the elements off reduces the load on the electrical system vs having it on all the time because the comfort level can't be reached. I guess there 2 schools at thought in play here.Isn't that better though.. not sure how good a feature is that only works for a few minutes and then is too uncomfortable and has to be turned off.