1999 GMC Sonoma Owner's Manual - Page 62

yellowblue Door Locks CAUTION: Unlocked doors can be dangerous. Passengers -- especially children -- can easily open the doors and fall out. When a door is locked, the inside handle won't open it. Outsiders can easily enter through an unlocked door when you slow down or stop your vehicle. This may not be so obvious: You increase the chance of being thrown out of the vehicle in a crash if the doors aren't locked. Wear safety belts properly, lock your doors, and you will be far better off whenever you drive your vehicle. There are several ways to lock and unlock your vehicle. You can use the keyless entry system, if you have this feature. You can use your key to unlock your door from the outside. To lock your door from the inside, slide the lever on your inside door down. To unlock the door, slide the lever on your inside door up. You will see a red area on the lever. 2-4