Bought a used 2007 Avalanche which came with only one remote. The quality of this unit is 99/100 as good as the factory remote fob. Teaching the truck was simple, but the instruction sheet that came with the remote was missing one critical word ... ""simultaneously"". Once the truck is ready to learn the new remote, press the Lock and Unlock buttons ""simultaneously"" until the truck chimes twice. The Avalanche owner's manual was clearer on the procedure.