2003 GMC Sierra 1500 Pickup Owner's Manual - Page 367

Turn Signals When Towing a Trailer The arrows on your instrument panel will flash whenever you signal a turn or lane change. Properly hooked up, the trailer lamps will also flash, telling other drivers you're about to turn, change lanes or stop. When towing a trailer, the arrows on your instrument panel will flash for turns even if the bulbs on the trailer are burned out. Thus, you may think drivers behind you are seeing your signal when they are not. It's important to check occasionally to be sure the trailer bulbs are still working. You may also want to activate the tow/haul mode if the transmission shifts too often. See Tow/Haul Mode Light on page 3-48. If you have a 5-speed manual transmission and you are towing a trailer, it's better not to use FIFTH (5) gear. Just drive in FOURTH (4) gear (or, as you need to, a lower gear). If you have a 6-speed manual transmission and you are towing a trailer, it's better not to use SIXTH (6) gear. Drive in FIFTH (5) gear (or, as you need to,a lower gear). When towing at high altitude on steep uphill grades, consider the following: Engine coolant will boil at a lower temperature than at normal altitudes. If you turn your engine off immediately after towing at high altitude on steep uphill grades, your vehicle may show signs similar to engine overheating. To avoid this, let the engine run while parked (preferably on level ground) with the automatic transmission in PARK (P) (or the manual transmission out of gear and the parking brake applied) for a few minutes before turning the engine off. If you do get the overheat warning, see Engine Overheating on page 5-36. Driving On Grades Reduce speed and shift to a lower gear before you start down a long or steep downgrade. If you don't shift down, you might have to use your brakes so much that they would get hot and no longer work well. If you have an automatic transmission, you can tow in DRIVE (D). You may want to shift the transmission to lower gear selection if the transmission shifts too often (e.g., under heavy loads and/or hilly conditions). 4-86