i went through the same shit with my 2019 trail boss leaving it at dealer for weeks at a time with them saying they cant find anything and its not happening when they have it.call GMC THERE NO HELP. after 10 months for the back and forth i got feed up and traded it in taking a $3500,00 loss plus 10 months worth of payments down the drain . and got a 2020 trail boss ...its sad that i had to trade in a 10 month old truck with 4700 miles on it and GM not do a thing to make it right.
p,s, lemon law lawyer was a joke said it would take 2 years