GMC 2008 Envoy Denali Owner's Manual page 93

When trying to start the vehicle, if the engine does not
start and the security light comes on, there may be
a problem with your theft-deterrent system. Turn
the ignition off and try again.
If the engine still does not start, and the key appears to
be undamaged, try another ignition key. At this time,
you may also want to check the fuse. See Fuses
and Circuit Breakers on page 5-110. If the engine still
does not start with the other key, your vehicle needs
service. If your vehicle does start, the first key may be
faulty. See your dealer/retailer who can service the
theft-deterrent system and have a new key made.
It is possible for the theft-deterrent system decoder to
learn the transponder value of a new or replacement
key. Up to 10 keys may be programmed for the vehicle.
The following procedure is for programming additional
keys only.
Canadian Owners: If you lose or damage your keys,
only a dealer/retailer can service the theft-deterrent
system to have new keys made. To program additional
keys you will require two current driver's keys.
To program a new key do the following:
1. Verify that the new key has PK3+ stamped on it.
2. Insert the current driver's key in the ignition
and start the engine. If the engine will not start
see your dealer/retailer for service.
3. After the engine has started, turn the key to
LOCK/OFF, and remove the key.
4. Insert the second current driver's key in the ignition
and start the engine within ten seconds of removing
the previous key. If the engine will not start see
your dealer/retailer for service.
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