Backup camera backup camera guidelines.
 

I have a 2016 Chevy Silverado 3500 LTZ. I removed the tailgate and disconnected the backup camera. After doing this, when I shift to reverse the blank blue screen comes up with the message " service camera" as to be expected. However, the backup guidelines now point/curve upward instead of being parallel to the road surface as normal. The lines still respond to turning the steeering wheel as normal. I reconnected the camera but the guidelines are still pointing upward, skyward instead of parallel to the road surface. I had the dealership look at this, I was told they have no information for this issue and no solution. I would appreciate help with this issue.