Got an "Important Update" via my cell phone about an hour ago, I punched the button to update via the infotainment system, went to the Yukon and started it up, clicked on the settings icon and it asked to install the update and directed me to turn off the vehicle and leave it parked (it was in my garage). Said it might take 15 minutes, so I went inside. In about 6-7 minutes I received another alert that the update was successful!. I have no idea what this did as I never had the issue with the HVAC slowing down on startup and my Yukon still blows at high when started after the update, hope maybe it cured those of you that had that issue?