Hi everyone. New XT5 owner and contributor from Toronto. Third time Caddy owner with lots of other vehicles in between. Just turned 3000 miles. While driving we experienced a hesitation at a light then it bucked on us. Within 10 minutes I received an OnStar email warning of possible engine and transmission failure. Check engine light is on. Driving characteristics are normal.
In reading other posts from 2016-2017. I read about recurring engine code issues. They changed sensors and entire shift levers with multiple reprogramming to no avail. If anyone heard about this legacy issue don't be shy. As I'm taken through the process I'll keep you up to date.

Welcome to the forum and sorry to hear that you're already having transmission issues with your XT5. Its the first I've heard of any issues with the 2018MY. Has your dealer given you any indication of what they think a possible fix could entail?

I find that sometimes it helps to get an opinion from different dealerships because some might go beyond the book and do their own analysis of what could be wrong.
But if you're already going to a reputable dealer then you might already be one step ahead.