hyperv6, thanks for sharing the above information. It's good to see that GM finally came out with a TSB on this issue. The "negative effects on cabin comfort" listed in TSB #19-NA-177 are already happening with my truck. It is the least comfortable AC I've ever experienced, so I don't have much to lose in having them reprogram the control module. It may be several days before I can take it in, but I will update here afterwards.