I took the Yukon back to a different dealer today. The tech disabled the Onstar device as planned which did kill the WiFi signal. There were no error messages on the console afterward, such as the air bags and stability control appeared to be working. I left the dealership... and soon after noticed the compass displayed "cal" as in calibrate, and then about a half mile down the road the Navigation system displayed a "GPS" icon with a red x through it.
I took it back to the dealer and he said he would have to e-mail GM and see what they have to say about it. He offered to reconnect it in the meantime, but I told him to just skip it for now and we could deal with it later. I am really happy I did that now, because several strange issues have been resolved.
1. I had hardwired my old garmin GPS in the Yukon as the built-in nav sucks. The old Garmin worked great in the other vehicles, but it always had a hard time finding a gps signal in the Yukon. I assumed it was the windshield, as some are coated with metal which blocks the GPS signal. Often driving down the road it would say "GPS lost" and under the best circumstances, I would only get a couple bars on the GPS strength meter. After the On-Star device was disabled, the Garmin GPS displayed a 5 bar signal strength and has worked perfectly ever since.
2. I used to have to drive right up to the garage door before the operator would work. After the On-Star device was disabled, the operator will now open the garage door before turning into our long driveway.
3. We would have cell phone quality issues from time to time. Low signal strength, and static were some of the issues. The phone has great signal now and the calls are crystal clear.
4. The original business phone issues are completely gone now. We can leave the vehicles running all day and not a single issue with the phone system now.
I kind of expected the compass to break when they killed the Onstar. The navigation system still works, but right below the time in the upper right corner, there used to be the direction indicator. It now displays a big "GPS" icon with a red x going through it. It also displays the calibrate compass icon at the top. The navigation is usable, but is riddled with error messages. The compass on the dash display around the digital speedometer at first said "Cal", but the error has went away now and it just no longer displays the direction I am heading. I used the compass, but it is not a deal breaker and the positive out weights it missing, but I hope that we can figure out a way to rid the error messages on the infotainment center. I will probably live with the errors, but it does not seem like I should have to.