Picked up a new Z, tire pressure not reporting for one wheel :(

[03Touring6]

Hello, I recently picked up an '03 Z touring 6-speed, and noticed that one of my rear wheels is not reporting the tire pressure to the computer display. The readout displays 32-32 for the front, but 31- -- for the back. Should I just take it to a dealer or buy a sensor online to have them put in? I already got burned once by purchasing a key FOB from the dealer for $108 and then finding out that they are like $20 on ebay so I thought i'd ask around to see if anyone else had this problem. It's not a huge deal, I just think it's really cool to see the tire pressures and don't want to have anything broken in the car. Thanks!
Modified by 03Touring6 at 4:02 PM 6/18/2009

[evildky]

I'd call tirerack

[03Touring6]

Thanks, will do. That is the only place I buy tires.