GM Service Manual Online
For 1990-2009 cars only

Lockout Protection for Chevrolet Avalanche - 2WD 2003

This feature protects you from locking your key in the vehicle when the key is in the ignition 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 unlock.