1994 GMC Sonoma Owner's Manual - Page 184

Hazard Warning Flashers Your hazard warning flashers let you warn others. They also let police know you have a problem. Your front and rear turn signal lights will flash on and off. Press the button in to make your front and rear turn signal lights flash on and off, Your hazard warning flashers work no matter what position your key is in, and even if the key isn't in. To turn off the flashers, pull out on the collar. When the hazard warning flashers are on, your turn signals won't work. 5-2