i have a 2007 grand prix, while iw as driving last night my tire light started blinking and my information center said "service tire pressure monitring system" i went threw the information to see if my tire pressure was still showing but it was not. it just shows dashes, im trying to figure out if i would need to replace my whole system of if its just one of the pressure gauges in one of my wheels, how would i find out which one it is?