GM Service Manual Online
For 1990-2009 cars only
  1. Place the floor shift lever in the PARK position.
  2. Turn the column lock cylinder to the LOCK position.
  3. If the center console is in place, remove the "pencil tray" from in front of the shift control.
  4. Important: 

       • The key must not be able to be removed from the ignition cylinder with the transmission control lever in any position other than PARK. If they key can be removed in any other position, adjustment or repair is necessary.
       • The shift lever must not move from park unless the key is in the ON position. If the lever can be removed from park with the key in the OFF position, adjust or repair the park lock cable.

  5. While using a small screwdriver to release the adjuster lock tang, rotate the threaded cable adjuster until three threads are showing.
  6. Re-check park lock operation. If park lock does not function, fine tune the cable 1/2 turn at a time until the proper operation is achieved.