2003 Lexus SC 430 Tire Pressure Monitor/Sensor

My car has Michellin run-flat tires (PS2). I am getting a tire pressure warning lamp (steady on, no chimes) that would normally indicate low pressure. All tires are at exact correct pressure. I suspect that one of the tire pressure sensors may be defective or some other part of the system. How might I trouble shoot this problem? Do the sensors have a battery that needs to be replaced? How does one replace a sensor and then reset the system? Thanks.