Wish I never read this post...now I am confused.
First of all the compact spare is not part of the tire pressure monitoring system (per the manual). I guess if you have a full size spare, it would be.
Also, the monitoring system uses as a benchmark what ever the tire pressure is when the system is reset. It doesn't say, but I would assume maybe a 10% loss of pressure would set off the warning light. So, if the dealer put 30 pounds in each tire and set the system, then 27 psi would set off the light.
Now, here is what I don't understand. I recently replaced all four tires at an independent shop. The manual says that you need to replace the warning valves and transmitters, which was done. It also says you need to register the new ID codes using the switch under the glove box. The push button pin has two settings....main & 2nd. The main is for the tires installed at the factory. The second is for any new warning valves/transmitters. Well, mine is still on Main. So, I don't know if I need to put it on 2nd, and then reset the monitoring system using the button under the steering wheel.
I guess my confusion is whether the 2nd position is for a second set of tires...say winter tires.
Any ideas?