2007 Chevrolet Express Van Owner's Manual - Page 277

If you do, then be sure to seal the holes later when you remove the hitch. If you don't seal them, deadly carbon monoxide (CO) from your exhaust can get into your vehicle as well as dirt and water. See "Carbon Monoxide" under Engine Exhaust on page 132. Trailer Brakes If your trailer weighs more than 1,000 lbs (450 kg) loaded, then it needs its own brakes - and they must be adequate. Be sure to read and follow the instructions for the trailer brakes so you'll be able to install, adjust and maintain them properly. Since your vehicle is equipped with StabiliTrak®, your trailer brake system cannot tap into the vehicle's hydraulic brake system. Safety Chains You should always attach chains between your vehicle and your trailer. Cross the safety chains under the tongue of the trailer to help prevent the tongue from contacting the road if it becomes separated from the hitch. Instructions about safety chains may be provided by the hitch manufacturer or by the trailer manufacturer. Follow the manufacturer's recommendation for attaching safety chains and do not attach them to the bumper. Always leave just enough slack so you can turn with your rig. Never allow safety chains to drag on the ground. 277