*UPDATE* I had the harness pinned out that is supposed to carry the VSS signal from the Electronic Brake Control Module. GM did not include that wire in the harness. I'm assuming because they never set up the vehicle to have a navigation radio. I put some feelers out to some people I know to see if the vehicle speed signal would still come off of the EBCM if a wire was added to the harness in the correct pin location which could then be tied directly into the radio. Worst case scenario I've been told would be to run a wire from each wheel speed sensor, tie them together, and then tie that into the radio. I'm holding off on that for now, but we'll see what happens.