I tow a 2004 Envoy XUV. If you don't have the manual. (this is in manual)
4 wheel drive. Position vehicle. Put Emergency BRAKE ON 1. Turn ignition key on. 2. put shift selector in neutral. 3. Turn electronic 4wheel drive switch all the way to the right and hold it until you hear the audible "slide" of the trans going into neutral. (about 10 seconds), 4. Put shift selector in Park, ( yeah I know, scared me too, but thats what I been doing for 9 years) 5 Make sure all windows are up and take ignition key out. (don't ask me how I know about the windows)
6. remove fuses #2 and 5 under black square fuse box located under the hood in engine compartment drivers side. 7. release parking brake. ( I use a brake buddy) 8. drive away
Once you move the 4 wheel drive selector and hear it shift, you wanna be careful cause your vehicle will now roll freely with the parking brake off.