Chevrolet TrailBlazer Owner's Manual page 194

Lock Doors
Press the customization button until LOCK DOORS: IN
GEAR appears in the display. To select your
preference for automatic locking, press the select button
while LOCK DOORS: IN GEAR is displayed on the
DIC. Pressing the select button will scroll through the
following choices:
LOCK DOORS: IN GEAR (default): The doors will lock
when the vehicle is shifted out of PARK (P).
LOCK DOORS: WITH SPEED: The doors will lock
when the vehicle speed is above 8 mph (13 km/h) for
three seconds.
For more information on automatic door locks, see
Programmable Automatic Door Locks on page 2-10.
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Unlock Doors
Press the customization button until UNLOCK
DOORS: IN PARK appears in the display. To select
your preference for automatic unlocking, press the select
button while UNLOCK DOORS: IN PARK is displayed
on the DIC. Pressing the select button will scroll through
the following choices:
UNLOCK DOORS: IN PARK (default): All of the doors
will unlock when the vehicle is shifted into PARK (P).
UNLOCK DRIVER: IN PARK: The driver's door will be
unlocked when the vehicle is shifted into PARK (P).
UNLOCK DOORS: KEY OUT: All of the doors
will unlock when the key is taken out of the ignition.
UNLOCK DOORS: MANUALLY: The doors will not be
unlocked automatically.
Choose one of the available options and press the
customization button while it is displayed on the DIC to
select it and move on to the next feature. For more
information on automatic door locks, see Programmable
Automatic Door Locks on page 2-10.