2001 Chevy Silverado WINDOW

This is a very common problem with the silverado. The driver's side window gets used the most. The motor/actuator that raises & lowers the window does so by means of a track, sliders and wound steel cables attached to the motor. Assuming that you are getting power to the motor via the switch (12v test light) for the up position, I would say it is the braided steel cable(s). They get worn, some strands will snap leaving free ends that will wrap around the good portion of the cable and create a knot. The motor has enough torque to pull the window down but not enough torque to pull the window up because the knot will lodge into the guide hole of the motor assembly. You can't replace just the cables, you have to buy the whole actuator assembly/motor unit as a set.