Bonnevilles 2000-2005 all use the class 2 Data-bus system along with a ton of other GM vehicles.
How can you check ?
Pull the factory radio and checking to see if there is a ribbon cable on the back of the deck, if there is it'* a Data-bus system.
What does this mean for your aftermarket radio install ?
just tap into those wires for power etc. because they are data
, not regular power.
There is also a possability that the ignition harness in those cars could also be muti-plex (Data) just like in the newer Benz, Bmw etc.
If you don't buy the appropriate module or wiring harness, the following are the functions you will loose & more.....
-Chimes; door ajar, seat belt etc.
-Warnings; Low oil pressure, Low fuel, Hi-Temp, etc.
-Possibly of Air Bags not functioning
-Partial Diagnostic Loss
-RAP (The radio will not stay on until you open the door) - Not 100% sure about this one.
The correct part number for your vehicle is GMC02
It is a module, Not a relocation harness like is availble for other GM'*.
This part is available from Best Buy etc.
If you want to find out more info go to this link:
If I were you, I would spend the money and bite the bullet its better than loosing all those functions and screwing up your car.
Its not like your getting rid of the car or aren't going to spend money on other repairs down the road.
Just my opinion as a Installer,