Pontiac 2005 Montana Owner's Manual page 111

Dual Sliding Doors Sliding Door Lock
To open either sliding door from outside the vehicle, pull
the handle out and then pull the door toward the rear.
If you slide the door all the way back, the door will rest in
a detent position.
To move the door forward, you must first pull the door
past the open detent position.
The driver's side sliding door is designed to open
only a little if the fuel door is open. If this ever happens,
don't try to force the sliding door. Just close the
driver's side sliding door. Then when the fuel filler
door is closed, the driver's side sliding door can be
opened normally.
2-13