One problem related to underbody shield has been reported for the 2003 Chevrolet Suburban. The most recently reported issues are listed below.
Brake pedal almost to floor, extremely long time to stop. No warning just driving in columbus traffic and lost brakes. Found master cylinder almost empty. Brake lines rusted through left side drivers floor/frame rail area. Dealer estimate $1200 to$1600. Seems to be a common problem as on line investigation verifies. Web site shows open case,no re-call to repair.