Thanks for the replies. I have checked the other threads and as mentioned in your notes, I have had the dealer reset the sensors, but this has not solved the problem. Do I need to assume that they didn't actually reset them or that there is something wrong with the installation on my full size spare or one of the other tires?

The other thing that seems strange is that the alarm comes in on seemingly random times when driving, which makes me think that the problem is with one of the sensors or the way it was installed.