1998 GMC Sonoma Owner's Manual - Page 209

Making Turns Turn 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 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 aboutto 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 tobe sure the trailer bulbs are still working. NOTICE: Making very sharp turns while trailering could cause the trailer to come contact with the in vehicle. Your vehicle could be damaged. Avoid making very sharp turns while trailering. When you're turning with a trailer, make wider turns than normal. Do this so your trailer won't strike soft shoulders, curbs,road signs, trees or other objects. Avoid jerky or sudden maneuvers. Signal well in advance. 4-53