Vehicle Communication Interface Module (VCIM) (Onstar®)
WARNING: This page is about a different car, the 2006 Buick Lucerne. However, it is still accessible from the selected car via links, so may be relevant.
VCIM RAP activation/termination is the same as radio operation with 1 exception; if there is an active call when the ignition key is turned off the VCIM will remain in RAP mode and keep the radio in RAP mode until the call is terminated.