Ordered four to put on new Tesla Model S wheels. Only two wheels showed pressure readings and only intermittently (after 20 miles on the freeway). I emailed the seller several times, who quickly replied that the machine was still "learning". Went back to Discount Tire who found that two of the four sensors were not sending out a signal. I wrote to the seller twice, no response. He ended up spending over $400 to have the dealer diagnose and install two new sensors.