I just had new brakes and rotors put all the way around my 90 420sel. I thought my car had rear sensors that would light up a light on the dash when the pads needed to be replaced. The mechanic stated that my car did not have sensors on the back brakes. Could this be true? I thought all 420sel's had the sensors. Is it just an option? I am thinking my wife has sensors on her 89 300se on front and back. Can anyone help me get this straight?