2005 GMC Envoy Owner's Manual - Page 407

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 5-78 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 below. {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 spare. 5-75