GM Service Manual Online
For 1990-2009 cars only
  1. With the power roof closed, place the tailgate in the down position. Using a hose or high-pressure sprayer, spray the entire length of the metal rail to remove any accumulated dirt or debris.
  2. Open the power roof half-way. Spray the rear end of the metal rail to remove any remaining dirt or debris.
  3. Open the power roof completely. Then close the power roof to ensure that all dirt and debris has been removed from the system.
  4. Repeat as necessary.