When a tire is low and the warning comes on, how do I know WHICH tire is low? Also, why does the pressure rise in the spare tire along with the other four after driving a while? This happens even in cold weather.

Seems to be a real design flaw on the LS - although I do believe it is a live system so you could try letting each tyre down a bit in turn and see which warning comes up?

No idea why the pressure in the spare will be changing, I suppose in cold weather it probably makes sense as the heat from the car will filter into the boot but surely shouldn't be getting as warm as the tyres on the car?