I have a 2004 Chrysler Pacifica FWD with 45,000 miles. After having the tires rotated, the "Service Tire System Soon" display came on and stayed on. The Tire dealer tried to reset the display but could not. I also have a plug-in analyzer, but it tells me everything checks out OK. I'm reluctant to bring it to the dealer at this point to have new sensors installed in the valve stems (NAPA quoted me something like $45 each. Since I'll likely need to purchase tires in the next 15,000 miles or so I though I'd wait, but it's driving me crazy. The tires take 33 psi so I thought I'd do a little test myself before purchasing new sensors. I lowered the tire pressure on each tire individually (not all 4 at the same time) thinking I could identify which sensor(s) are in need of replacement. Much to my surprise, each time I lowered the pressure, the display would say 1 tire low. So now I'm wondering what is actually in need of repair or replacement here? The car has a space saver spare which does not have a sensor. Just to be sure, I filled the space saver spare to the recommended pressure before I did the test. Can anyone help?