Lights Flash at Lock
WARNING: This page is about a different car, the 2003 Cadillac CTS. However, it is still accessible from the selected car via links, so may be relevant.
This feature allows the exterior lamps to flash once when the remote keyless entry transmitter is used to lock the vehicle. All doors must be closed for this feature to work, and the lamps will not flash if the parking lamps or headlamps are on.