GMC 2003 Sierra - Manual (Page 99)

Rear Door Security Locks
(Crew Cabs)
Wfth this fEjpiure, you can thg rear side doors so that
they cannot be opened from the Inside by passengers.
This fsaiure Is iocated on tbs inside edge of the roar
doors.
1 To use one oi the locks do fhe following:
2. Open one oi the tear doors.
3. To errgage the near door sgcurity lock, move the
fever forward.
4. To disengage the lock, move the lever rearward.
5. Close the door.
6. Do the same Ihmg to the other rear door.
Thfl rear doors of your vehicle Cdnnol be opened from
the inside when ihis feature is in use. If you want to
open the rear door white the security lock Is engaged,
unlock ihe door and open the door from the outside.
Lockout Protection
This feature protects you from locking your key in the
vehicle when ihe kay is Jn the ignilion and a door
Is open.
If the power lock switch is pressed when a door is open
and the key is in the ignition, all of the doors will lock
and then the driver's door will unloch.