GM Service Manual Online
For 1990-2009 cars only

When locking the doors with the power lock switch and a door or the liftgate is open, the doors will lock five seconds after the last door is closed. You will hear three chimes to signal that the delayed locking feature is in use.

Pressing the power lock switch twice or the lock button on the RKE transmitter twice will override the delayed locking feature and immediately lock all the doors.

This feature will not operate if the key is in the ignition.

This feature can be programmed by using the Driver Information Center (DIC). See "DELAY DOOR LOCK" under DIC Vehicle Customization.