There is a sensor knob under little silver flip up box on the 153IR . Turn your sensor up til train detects it. A lot of cars are dark colored and some engines are to and plus some engines set up to high the 153IR won't pick it up. What i do set up the 153IR on a  block of wood or use reflective tape on my engines so the 153IR will pick up engine . The cars once turn sensor up not have to do anything to them.