Automatic side door wont work automatic - 2001 Pontiac Montana

Check the electrical spring connectors at the door, and the contacts at the door pillar. They are notorious for corrosion. Take some steel wool or very fine sand paper, rub against the contact areas until a copper color returns. The pillar contacts get corrosion and very poor continuity thru the connector. The spring contacts in the door can also get corrosion on the back side at the connector, try cleaning them on the outside first before attempting to remove door panel.