2005 Hummer H2 Owner's Manual - Page 302

Press the button on the instrument panel to the right of the steering wheel to enable the tow/haul mode. Press the button again to turn off tow/haul mode. The indicator light on the instrument panel will turn off. The vehicle will automatically turn off tow/haul mode every time it is started. Driving with tow/haul mode activated without a heavy load or with no trailer will cause reduced fuel economy and unpleasant engine and transmission driving characteristics, but will not cause damage. Weight of the Trailer How heavy can a trailer safely be? A light on the instrument panel will illuminate to indicate that tow/haul mode has been selected. It depends on how you plan to use your rig. For example, speed, altitude, road grades, outside temperature and how much your vehicle is used to pull a trailer are all important. And, it can also depend on any special equipment that you have on your vehicle. 4-70