Under the Frame Rail Reinforcements
WARNING: This page is about a different car, the 2008 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
IMPORTANT:
The jack stands must not contact the rocker panels, the floor pan, or the stone guard moldings. Remove the jacking covers from the rocker panels if necessary.
Position the jack stand under the frame rail reinforcements.