2004 GMC Sierra 1500 Pickup Owner's Manual - Page 512

Secondary Latch System Your vehicle has an underbody mounted tire hoist assembly equipped with a secondary latch system. It's designed to stop the spare tire from suddenly falling off your vehicle. For the secondary latch to work, the spare must be installed with the valve stem pointing down. See "Storing a Flat or Spare Tire, Jack and Tools" earlier in this section. {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. A. Push and Pull B. Rotate Tire 7. Make sure the tire is stored securely. Push, pull, and then try to rotate or turn the tire. If the tire moves, use the wheel wrench to tighten the cable. Reinstall the spare tire lock (if equipped). 5-112