GMC 2009 Yukon XL Owner's Manual page 44

Q:
What is wrong with this?
A:
The shoulder belt is too loose. It will not give as
much protection this way.
1-38
CAUTION:
{
You can be seriously hurt if your shoulder belt is
too loose. In a crash, you would move forward too
much, which could increase injury. The shoulder
belt should fit snugly against your body.