2003 GMC Sierra 1500 Pickup Owner's Manual - Page 116

Tow/HauI Mode (Automatic Transmission) Overdrive Disable (Allison Transmissions) r Your vehicle may be equipped with a tow/haul mode. The selector button is located on the end of the column shift lever. You can use this feature to assist when towing or hauling a heavy load. Turn tow/haul on and off by pressing the buttonuntil the tow/haul indicator light illuminates on the instrument panel. See "Tow/Haul Mode" under Towing a Trailer on page 4-66 for more information. If your vehicle has an Allison Transmission you may have the overdrive disable feature. The overdrive disable feature prevents the transmission from shifting into fifth (5) gear. The selector button is located on the end of the column shift lever. You can turn overdrive disable on and off by pressing and holding the button at the end of the column shift lever until the indicator light, on the instrument panel, illuminates. 2-29