Do they have to be in a tire in order to read? I bought a set of Rubicon wheels, and tires=no TPMS light at 35PSI. I sold my original tires, and the guy didn't want the rims. He gave me back the rims, and handed me the five sensors he took off so they didn't get damaged. I put them in my pocket, and forgot about them. I drove around that afternoon with them in my pocket, no TPMS light.