GM Service Manual Online
For 1990-2009 cars only

The fixed mast antenna can withstand most car washes without being damaged. If the mast should ever become slightly bent, you can straighten it out by hand. If the mast is badly bent you should replace it.

If the mast becomes loose from the antenna base, which is located on the fender, tighten by hand, then with a wrench, one quarter turn.