GMC 2009 Sierra 1500 Crew Cab Owner's Manual page 35

Q:
What is wrong with this?
A:
The belt is twisted across the body.
CAUTION:
{
You can be seriously injured by a twisted belt. In a
crash, you would not have the full width of the belt
to spread impact forces. If a belt is twisted, make
it straight so it can work properly, or ask your
dealer/retailer to fix it.
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