2003 GMC Sonoma Owner's Manual - Page 78

This vehicle has one double-sided key for the ignition and door locks. It will fit with either side up. The key code number tells your dealer or a qualified locksmith how to make extra keys. Keep this number in a safe place. If you lose your keys, you'll be able to have new ones made easily using this number. Your dealer should also have this number. Notice: Your vehicle has a number of features that can help prevent theft. You can have a lot of trouble getting into your vehicle if you ever lock your keys inside. You may even have to damage your vehicle to get in. So be sure you have spare keys. When a new vehicle is delivered, the dealer provides the owner with a pair of identical keys and a key code number. If you ever do get locked out of your vehicle call the GM Roadside Assistance Center. See Roadside Assistance Program on page 7-6 2-3