Had a dashboard warning light that kept going on my new car telling me I had an under inflated tire. For the life of me my tires looked fine and they had the proper pressure in them. Thinking that I possibly had a sensor issue or I was simply crazy and couldn't read a pressure gauge, I stopped over to have one of the guys check my tire pressure. Sure enough, he checked the pressure in all 4 tires and they had the correct pressure. About that time I am getting prepared for them to tell me my tire pressure sensor is bad, the mechanic said I know what it is... Apparently my spare has a tire pressure sensor (who knew) and after pulling off the tire cover and adding 15lbs of air, problem solved. Simple solution to a problem that most would never guess! I suppose that is why they are the experts.