Tire pressure monitor system

I have an '07 Monte Carlo with the tire pressure monitor system. It appeared to be working fine, but kept showing the right rear tire low. I had a Les Schwab dealership remove and patch the tire. It now holds air, but ever since, the system displays 1 PSI on the right rear tire and a yellow warning light stays lit.
Is there a particular position the tires must be mounted in to have the system function properly?
Thanks

there is a good chance the dealer might have broken the sensor when dismounting the tire.they should have relearned the tpm when they put the tire back on,I always do.any sensor that can't be relearned has to be replaced.this vehicle should still be under warrenty,I would go back and have them look at it again.it worked when it came in,it should work when it left.this is the tool they should have used to relearn it. http://gsi.xw.gm.com/image_en_us/gif/000/002/033/2033219.gif