My tire pressure sensor is very sensitive. I went to check it to see if I needed air. I assume (bad word) you are supposed to pull the insert out, but I could not figure out how to do it with out excessive force (nothing in the manual). As the tire stem is set deep into a little hole ( the engineer must not have tried to unscrew the cap) I had to get out a pair of needlenose pliers, turn and remove the cap, add a stem extender and was able to do the maintenance. I wish there was a "socket wrench" for tire stem caps.