Now to TRY to answer your question. My XT is capable of recognizing 5 different wheels. It takes maybe 3 miles of driving, then the pressure is displayed. I am NOT sure about other models and years.
Initially I was told to go to the dealer and have them program in the new wheel, and it will be in the history list, or whatever the CPU calls it. The first time I added the new wheel, I was driving to the dealer, then BAM it found the new wheel.
After that each wheel rotation, it took maybe 3 miles to identify all 4 wheels on the ground.
Hope this helps.
Oooops I am back…… I do believe that the very 1st time, I did the rotation, and added the new wheel, that I received some sort of message, on the cluster, advising me to contact the dealer. That was the first time it learned (I believe they use that term), of the new wheel.
OK, I screwed up. I just looked at all my maint records. I did have the dealer program the NEW wheel into the CPU. That was maybe 2.5 years back. Since then, the CPU will relearn the positions of any 4 of the 5 wheels, that are on the ground. SORRY for the confusion. 
