2004 Buick Rendezvous Owner's Manual - Page 146

Hazard Warning Flashers The hazard warning flasher button is located on top of the steering column. Your hazard warning flashers work no matter what position your key is in, and even if the key isn't in. Press the button to make the front and rear turn signal lamps flash on and off. Press the button again to turn the flashers off. When the hazard warning flashers are on, the turn signals won't work. Your hazard warning flashers let you warn others. They also let police know you have a problem. Your front and rear turn signal lamps will flash on and off. 3-6