I know this is an old thread but hopefully someone will have some input now. I recently bought a used 2019 2500HD that has this exact problem. I have the Service Trailer brake system error and reverse camera video loss. Looking for some help on where to start to avoid losing time and money.

 

check ground that is located behind the rt front tire. It’s a body to frame. My 2019 Silverados rust out in 40,000 miles and it caused lose of power steering and a trailer break code. The wire is braided copper and is exposed to water and salt from the road.No shield on the ire. I replaced mine with a shielded cable