GMC 2009 Sierra - Manual (Page 21)

Q:
What is wrong with this?
A:
The shoulder belt is too loose. It will not give as
much protection this way.
{ 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.
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