GMC 2003 C4C042 Owner's Manual page 81

If you ever lose your key, your dealer will be able to
assist you with obtaining a new one.
2-6
Your vehicle has one
-
double sided key for the
ignition and all door locks.
NOTICE:
Your vehicle has a number of new features that
can help prevent theft. But 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 extra keys.
If you ever do get locked out of your vehicle, call GM
Roadside Assistance Center. See "Roadside Assistance"
in the Index.