GMC 2008 Envoy - Manual (Page 386)

Secondary Latch System
Your vehicle has an underbody-mounted tire hoist
assembly equipped with a secondary latch system. It is
designed to stop the spare tire from suddenly falling off
your vehicle if the cable holding the spare tire is
damaged. For the secondary latch to work, the tire must
be stored with the valve stem pointing up. See Storing a
Flat or Spare Tire and Tools on page 5-96 for instructions
on storing the spare or flat tire correctly.
{ CAUTION:
Before beginning this procedure read all the
instructions. Failure to read and follow the
instructions could damage the hoist assembly
and you and others could get hurt. Read and
follow the instructions listed next.
{ CAUTION:
Someone standing too close during the
procedure could be injured by the jack.
If the spare tire does not slide off the jack
completely, make sure no one is behind you or
on either side of you as you pull the jack out
from the under spare.
To release the spare tire from the secondary latch:
1. Check under the
vehicle to see if the
cable is visible. If it is
not visible, proceed
to Step 6.
5-92