Unless I missed something I think you may have the wrong adapter. I just finished my install and used the GMOS-04 which retains the chimes and RAP features as well as integration with the Bose amp. attached is a short description.
Problem: Installing an aftermarket receiver in many late model (2000-up) General Motors vehicles means losing ONSTAR system functions, the Bose amplified speaker system, audible safety warnings, and the chime that warns the door is open.
Solution: Metra's GMOS-04 GM Class II data bus interface lets you replace the factory receiver in these vehicles without losing these functions. Connect your in-dash receiver to the GMOS-04 interface's RCA input jacks. You'll get the great sound you want, and keep these important features intact. The Bose amplified speakers and the ONSTAR system will operate with your new radio, as well as the door chime and audible safety warnings.
Also, once you turn off the ignition in these GM vehicles, the factory radio continues to play until you open the door. This interface maintains that function with your new aftermarket radio. This interface is compatible with select 2000-and up GMC, Chevrolet, Oldsmobile, Cadillac, Pontiac, Isuzu, and Hummer vehicles. Warranty: 1 year.
If I can be of any help please ask.