Check your owners manual, if it is like mine and says to adjust tire pressure back and forth for the tpms reset, then you have a direct system, Like I have. I think (haven't seen the tires off the rim) that our cars TMPS sensor is attached to the rim via a band that holds it in place. If the light hasn't come on at 40 PSI try driving around and get the speed up to at least 20 MPH. This is the speed that most systems activate and start scanning your tire pressure.