Buick 2001 Century Owner's Manual page 75

The ignition key is for the
ignition only.
The door key is for the
doors and all other locks.
The ignition and door keys don't have plugs.
Your dealer or Buick Roadside Assistance has the
code for your keys.
If you need a new ignition or door key, contact your
dealer who can obtain the correct key code. Also, see
"Roadside Assistance" in the Index for more information.
NOTICE:
Your vehicle has a number of 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.
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