2010 GMC Savana 2500 Cargo Owner's Manual - Page 258

Tow/Haul is designed to be most effective when the vehicle and trailer combined weight is at least 75 percent of the vehicle's Gross Combined Weight Rating (GCWR). See "Weight of the Trailer" later in the section. Tow/Haul is most useful under the following driving conditions: Driving with a Trailer { WARNING: When towing a trailer, exhaust gases may collect at the rear of the vehicle and enter if the liftgate, trunk/hatch, or rear-most window is open. Engine exhaust contains carbon monoxide (CO) which cannot be seen or smelled. It can cause unconsciousness and even death. To maximize safety when towing a trailer: • Have the exhaust system inspected for leaks and make necessary repairs before starting a trip. • Never drive with the liftgate, trunk/hatch, or rear-most window open. • Fully open the air outlets on or under the instrument panel. • Adjust the Climate Control system to a setting that brings in only outside air and set the fan speed to the highest setting. See Climate Control System in the Index. For more information about carbon monoxide, see Engine Exhaust on page 3-38 • When pulling a heavy trailer or a large or heavy load through rolling terrain. • When pulling a heavy trailer or a large or heavy load in stop and go traffic. • When pulling a heavy trailer or a large or heavy load in busy parking lots where improved low speed control of the vehicle is desired. Operating the vehicle in Tow/Haul when lightly loaded or with no trailer at all will not cause damage. However, there is no benefit to the selection of Tow/Haul when the vehicle is unloaded. Such a selection when unloaded may result in unpleasant engine and transmission driving characteristics and reduced fuel economy. Tow/Haul is recommended only when pulling a heavy trailer or a large or heavy load. Trailer Brakes A loaded trailer that weighs more than 1,500 lbs (680 kg) needs to have its own brake system that is adequate for the weight of the trailer. Be sure to read and follow the instructions for the trailer brakes so they are installed, adjusted and maintained properly. 5-34