Early 1997 models did have an external antenna on the rear fender or 1/4 panel, and while I have not heard ^^^^ that reason, it is plausable.

The only external antenna on the Grand Prix after 1997 was on the 2001+ models that had the Onstar option, and that antenna is mounted on the back drivers side glass.

Mid 1997 all radio antenna's were installed on the rear glass.

webracin