Chevrolet 2004 Impala Owner's Manual page 340

The tools you'll be using include the jack (A) extension
and protector/guide (B) and wheel wrench (C).
5-78
Removing the Wheel Covers and the
Wheel Nut Caps
Removing the Center Wheel Cap
To remove the wheel center cap use the flat end of the
wheel wrench and pry them off at the pry off notch.
Do not drop the cap or lay it face down, as it could
become scratched or damaged. The wheel nuts are
hidden behind the center cap.
Your vehicle may have
center caps if equipped
with aluminum wheels.