I had the same issue. I took it to my dealer, they are going to replace the whole thermostat box. He said it was a common issue and it is covered under my powertrain warranty. Only problem is that the product is 1-2 weeks out.I am having this issue now with my 2019 Acadia. Were you able to get the issue resolved?
According to my dealer this should be covered under the powertrain warranty. Mine is at the dealer right now getting fixed.I just replaced the battery and still am having this error message. I have a 2018 Acadia. Did they give you an estimate for the thermostat?