1997 GMC Sonoma Owner's Manual - Page 194

I'urn Signals When Towing a Trailer When you tow a trailer, your vehicle has to have extra wiring and a heavy-duty turn signal flasher (included in the optional trailering package). The arrowson your instrument panel will flash Properly whenever you signal a turn or lane change. 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 turnseven 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. On a long uphill grade, shift down and reduce your speed to around 45 mph (70 km/h) to reduce the possibility of engine and transmission overheating. If you have an automatic transmission, you should use DRIVE (D) when towing a trailer. Operating your vehicle in DRIVE (D) when towing a trailer will minimize heat buildup and extend the life of your transmission. Or, if you have a manual transmission, it's better not to use FIFTH ( 5 ) ,just drive in FOURTH (4) (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 engineoverheating. 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" in the Index. 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. 4-56